This document relates generally to time series analysis, and more particularly to structuring unstructured time series data into a hierarchical structure.
Many organizations collect large amounts of transactional and time series data related to activities, such as time stamped data associated with physical processes, such as product manufacturing or product sales. These large data sets may come in a variety of forms and often originate in an unstructured form that may include only a collection of data records having data values and accompanying time stamps.
Organizations often wish to perform different types of time series analysis on their collected data sets. However, certain time series analysis operators (e.g., a predictive data model for forecasting product demand) may be configured to operate on hierarchically organized time series data. Because an organization's unstructured time stamped data sets are not properly configured, the desired time series analysis operators are not able to properly operate on the organization's unstructured data sets.
In accordance with the teachings herein, systems and methods are provided for analyzing unstructured time stamped data of a physical process in order to generate structured hierarchical data for a hierarchical time series analysis application. A plurality of time series analysis functions are selected from a functions repository. Distributions of time stamped unstructured data are analyzed to identify a plurality of potential hierarchical structures for the unstructured data with respect to the selected time series analysis functions. Different recommendations for the potential hierarchical structures for each of the selected time series analysis functions are provided, where the selected time series analysis functions affect what types of recommendations are to be provided, and the unstructured data is structured into a hierarchical structure according to one or more of the recommended hierarchical structures, where the structured hierarchical data is provided to an application for analysis using one or more of the selected time series analysis functions.
As another example, a system for analyzing unstructured time stamped data of a physical process in order to generate structured hierarchical data for a hierarchical time series analysis application includes one or more processors and one or more computer-readable storage mediums containing instructions configured to cause the one or more processors to perform operations. In those operations, a plurality of time series analysis functions are selected from a functions repository. Distributions of time stamped unstructured data are analyzed to identify a plurality of potential hierarchical structures for the unstructured data with respect to the selected time series analysis functions. Different recommendations for the potential hierarchical structures for each of the selected time series analysis functions are provided, where the selected time series analysis functions affect what types of recommendations are to be provided, and the unstructured data is structured into a hierarchical structure according to one or more of the recommended hierarchical structures, where the structured hierarchical data is provided to an application.
As a further example, a computer program product for analyzing unstructured time stamped data of a physical process in order to generate structured hierarchical data for a hierarchical time series analysis application, tangibly embodied in a machine-readable non-transitory storage medium, includes instructions configured to cause a data processing system to perform a method. In the method, a plurality of time series analysis functions are selected from a functions repository. Distributions of time stamped unstructured data are analyzed to identify a plurality of potential hierarchical structures for the unstructured data with respect to the selected time series analysis functions. Different recommendations for the potential hierarchical structures for each of the selected time series analysis functions are provided, where the selected time series analysis functions affect what types of recommendations are to be provided, and the unstructured data is structured into a hierarchical structure according to one or more of the recommended hierarchical structures, where the structured hierarchical data is provided to an application.
The time series exploration system 102 can facilitate interactive exploration of unstructured time series data. The system 102 can enable interactive structuring of the time series data from multiple hierarchical and frequency perspectives. The unstructured data can be interactively queried or subset using hierarchical queries, graphical queries, filtering queries, or manual selection. Given a target series, the unstructured data can be interactively searched for similar series or cluster panels of series. After acquiring time series data of interest from the unstructured data, the time series data can be analyzed using statistical time series analysis techniques for univariate (e.g., autocorrelation operations, decomposition analysis operations), panel, and multivariate time series data. After determining patterns in selected time series data, the time series data can be exported for subsequent analysis, such as forecasting, econometric analysis, pricing analysis, risk analysis, time series mining, as well as others.
Users 104 can interact with a time series exploration system 102 in a variety of ways. For example,
Based on the recommendations made by the data structuring recommendations functionality, the unstructured time stamped data 304 is structured to form structured time series data 312. For example, the recommendation for a particular time series analysis function and set of unstructured time stamped data may dictate that the unstructured time stamped data be divided into a number of levels along multiple dimensions (e.g., unstructured time stamped data representing sales of products for a company may be structured into a product level and a region level). The recommendation may identify a segmentation of the time series data, where such a segmentation recommendations provides one or more options for dividing the data based on a criteria, such as a user defined criteria or a criteria based upon statistical analysis results. The recommendation may further identify an aggregation frequency (e.g., unstructured time stamped data may be aggregated at a monthly time period). The structured time series data 312 is then provided to a hierarchical time series analysis application 314, where a selected time series analysis 306 function is applied to the structured time series data 312 to generate analysis results 316 (e.g., a time slice analysis display of the structured data or analysis results).
Upon selection of a hierarchical structure and an aggregation frequency for a particular time series analysis function, the time series exploration system 402 structures the unstructured time stamped data 404 accordingly, to generate structured time series data 412. The structured time series data 412 is provided to a hierarchical time series analysis application 414 that applies the particular time series analysis function to the structured time series data 412 to generate analysis results 416.
The data sufficiency metric 510 that is associated with the selected optimal frequency is used to determine a data sufficiency metric the potential hierarchical structure at 514. Thus, the data sufficiency metric of the best candidate frequency may be imputed to the potential hierarchical structure or otherwise used to calculate a sufficiency metric for the potential hierarchical structure, as the potential hierarchical structure will utilize the optimal frequency in downstream processing and comparison. The performing of the hierarchical analysis 502 to identify an optimal frequency for subsequent potential hierarchical structures is repeated, as indicated at 516. Once all of the potential hierarchical structures have been analyzed, a data structure includes an identification of the potential hierarchical structures, an optimal frequency associated with each of the potential hierarchical structures, and a data sufficiency metric associated with each of the potential hierarchical structures.
At 518, one of the potential hierarchical structures is selected as the selected hierarchical structure for the particular time series analysis function based on the data sufficiency metrics for the potential hierarchical structures. The selected hierarchical structure 520 and the associated selected aggregation frequency 522 can then be used to structure the unstructured data for use with the particular time series analysis function.
The structured time series data can be utilized by a time series analysis function in a variety of ways. For example, all or a portion of the structured time series data may be provided as an input to a predictive data model of the time series analysis function to generate forecasts of future events (e.g., sales of a product, profits for a company, costs for a project, the likelihood that an account has been compromised by fraudulent activity). In other examples, more advanced procedures may be performed. For example, the time series analysis may be used to segment the time series data. For instance, the structured hierarchical data may be compared to a sample time series of interest to identify a portion of the structured hierarchical data that is similar to the time series of interest. That identified similar portion of the structured hierarchical data may be extracted, and the time series analysis function operates on the extracted similar portion.
In another example, the structured hierarchical data is analyzed to identify a characteristic of the structured hierarchical data (e.g., a seasonal pattern, a trend pattern, a growth pattern, a delay pattern). A data model is selected for a selected time series analysis function based on the identified characteristic. The selected time series analysis function may then be performed using the selected data model. In a different example, the selected time series analysis function may perform a transformation or reduction on the structured hierarchical data and provide a visualization of the transformed or reduced data. In a further example, analyzing the distributions of the time-stamped unstructured data may include applying a user defined test or a business objective test to the unstructured time stamped data.
Structuring unstructured time series data can be performed automatically (e.g., a computer system determines a hierarchical structure and aggregation frequency based on a set of unstructured time series data and an identified time series analysis function). Additionally, the process of structuring of the unstructured time series data may incorporate human judgment (e.g., structured judgment) at certain points or throughout.
The data structuring GUI 710 may be formatted in a variety of ways. For example, the data structuring GUI 710 may be provided to a user in a wizard form, where the user is provided options for selection in a stepwise fashion 718. In one example, a user is provided a number of potential hierarchical structures for the unstructured time stamped data 704 from which to choose as a first step. In a second step 722, the user may be provided with a number of options for a data aggregation time period for the hierarchical structure selected at 720. Other steps 724 may provide displays for selecting additional options for generating the structured time series data 712.
In the example of
As an example, a computer-implemented method of using graphical user interfaces to analyze unstructured time stamped data of a physical process in order to generate structured hierarchical data for a hierarchical forecasting application may include a step of providing a first series of user display screens that are displayed through one or more graphical user interfaces, where the first series of user display screens are configured to be displayed in a step-wise manner so that a user can specify a first approach through a series of predetermined steps on how the unstructured data is to be structured. The information the user has specified in the first series of screens and where in the first series of user display screens the user is located is storing in a tracking data structure. A second series of user display screens are provided that are displayed through one or more graphical user interfaces, where the second series of user display screens are configured to be displayed in a step-wise manner so that the user can specify a second approach through the series of predetermined steps on how the unstructured data is to be structured. The information the user has specified in the second series of screens and where in the second series of user display screens the user is located is storing in the tracking data structure. Tracking data that is stored in the tracking data structure is used to facilitate the user going back and forth between the first and second series of user display screens without losing information or place in either the first or second user display screens, and the unstructured data is structured into a hierarchical structure based upon information provided by the user through the first or second series of user display screens, where the structured hierarchical data is provided to an application for analysis using one or more time series analysis functions.
Functionality for operating on the unstructured data in a single pass 918 can provide the capability to perform all structuring, desired computations, output, and visualizations in a single pass through the data. Each candidate structure runs in a separate thread. Such functionality 918 can be advantageous, because multiple read accesses to a database, memory, or other storage device can be costly and inefficient. In one example, a computer-implemented method of analyzing unstructured time stamped data of a physical process through one-pass includes a step of analyzing a distribution of time-stamped unstructured data to identify a plurality of potential hierarchical structures for the unstructured data. A hierarchical analysis of the potential hierarchical structures is performed to determine an optimal frequency and a data sufficiency metric for the potential hierarchical structures. One of the potential hierarchical structures is selected as a selected hierarchical structure based on the data sufficiency metrics. The unstructured data is structured according to the selected hierarchical structure and the optimal frequency associated with the selected hierarchical structure, where the structuring of the unstructured data is performed via a single pass though the unstructured data. The identified statistical analysis of the physical process is then performed using the structured data.
Given an unstructured time-stamped data set 1004, a data specification 1006 applies both a hierarchical and time frequency structure to form a structured time series data set. The TSXENGINE 1002 forms a hierarchical time series data set at particular time frequency. Multiple structures can be applied for desired comparisons, each running in a separate thread.
The data specification 1006 can be specified in SAS code (batch). The data specification API 1008 processes the interactively provided user information and generates the SAS code to structure the time series data 1004. The data specification API 1008 also allows the user to manage the various structures interactively.
Because there are many ways to analyze time series data, user-defined time series functions can be created using the FCMP procedure 1010 (PROC FCMP or the FCMP Function Editor) and stored in the function repository 1012. A function specification 1014 is used to describe the contents of the function repository 1012 and maps the functions to the input data set 1004 variables which allow for re-use. These functions allow for the transformation or the reduction of time series data. Transformations are useful for discovery patterns in the time series data by transforming the original time series 1004 into a more coherent form. Reductions summarize the time series data (dimension reductions) to a smaller number of statistics which are useful for parametric queries and time series ranking Additionally, functions (transformations, reductions, etc.) can receive multiple inputs and provide multiple outputs.
The function specification 1014 can be specified in SAS code (batch). The function specification API 1016 processes the interactively provided user information and generates the SAS code to create and map the user-defined functions. The function specification API 1016 allows the user to manage the functions interactively.
Because there are many possible computational details that may be useful for time series exploration, the output specification 1018 describes the requested output and form for persistent storage. The output specification 1018 can be specified in SAS code (batch). The output specification API 1020 processes the interactively provided user information and generates the need SAS code to produce the requested output. The output specification API 1020 allows the user to manage the outputs interactively.
Because there are many possible visualizations that may be useful for time series exploration, the results specification 1022 describes the requested tabular and graphical output for visualization. The results specification 1022 can be specified in SAS code (batch). The results specification API 1024 processes the interactively provided user information and generates the need SAS code to produce the requested output. The results specification API 1024 allows the user to manage the outputs interactively.
Given the data specification 1006, the function specification 1012, the output specification 1018, and the results specification 1022, the TSXENGINE 1002 reads the unstructured time-stamped data set 1004, structures the data set with respect to the specified hierarchy and time frequency to form a hierarchical time series, computes the transformations and reductions with respect user-specified functions, outputs the desired information in files, and visualizes the desire information in tabular and graphical form.
The entire process can be specified in SAS code (batch). The time series exploration API processes the interactively provided user information and generates the need SAS code to execute the entire process. The system depicted in
Structured time series data and analysis results, as well as unstructured time stamped data, can be displayed and manipulated by a user in many ways.
Certain algorithms can be utilized in implementing a time series exploration system. The following description provides certain notations related to an example time series exploration system.
Let N represents the number of series recorded in the time series data set (or sample of the time series data set) and let i=1, . . . , N represent the series index. Typically, the series index is implicitly defined by the by groups associated with the data set under investigation.
Let tε{tib, (tib+1), . . . , (tie−1), tie} represent the time index where tib and tie represent the beginning and ending time index for the ith series, respectively. The time index is an ordered set of contiguous integers representing time periods associated with equally spaced time intervals. In some cases, the beginning and/or ending time index coincide, sometimes they do not. The time index may be implicitly defined by the time ID variable values associated with the data set under investigation.
Let s□{sib, . . . , sie} represent the season index where sib band sie represent the beginning and ending season index for the ith series, respectively. The season index may have a particular range of values, sε{1, . . . , S}, where S is the seasonality or length of the seasonal cycle. In some cases, the beginning and/or ending season index coincide, sometimes they do not. The season index may be implicitly defined by the time ID variable values and the Time Interval.
Let l=1, . . . , L, represent the cycle index (or life-cycle index) and Li=(tie+1−tib) represent the cycle length for the ith series. The cycle index maps to the time index as follows: l=(t+1−tib) and Li=(tie+1−tib)). The cycle index represents the number of periods since introduction and ignores timing other than order. The cycle index may be implicitly defined by the starting and ending time ID variable values for each series.
Let LP≦maxi (Li) be the panel cycle length under investigation. Sometimes the panel cycle length is important, sometimes it is not. The analysts may limit the panel cycle length, LP, under consideration, that is subset the data; or the analyst may choose products whose panel cycle length lies within a certain range.
Let yi,l represent the dependent time series values (or the series to be analyzed) where tε{tib, . . . , tie} to is the time index for the ith dependent series and where i=1, . . . , N. Let
represent the dependent time series vector for ith dependent series. Let {right arrow over (Y)}(i)={{right arrow over (y)}i}i=1N represent the vector time series for all of the dependent time series.
Let {right arrow over (x)}i,t represent the independent time series vector that can help analyze the dependent series, yi,t. Let {right arrow over (x)}i,t={xi,k,t}k=1K where k=1, . . . , K indexes the independent variables and K represents the number of independent variables. Let
represent the independent time series matrix for ith dependent series. Let X(t)={{right arrow over (X)}i}i=1N represent matrix time series for all of the independent time series.
Together, (yi,t,{right arrow over (x)}i,t) represent the multiple time series data for the ith dependent series. Together, (Y(t),X(t)) represent the panel time series data for all series (or a vector of multiple time series data).
Each historical dependent time series, yi,t, can be viewed as a cycle series (or life-cycle series) when the time and cycle indices are mapped: yi,t=yi,l where l=(t+1−tib). Let {right arrow over (y)}i={yi,l}l=1L
Each independent time series vector can be indexed by the cycle index: {right arrow over (x)}i,t={right arrow over (x)}i,l where l=(t+1−tib). Similarly {right arrow over (X)}i={{right arrow over (x)}i,l}l=1L
Together, (yi,l,{right arrow over (x)}i,l) represent the multiple cycle series data for the ith dependent series. Together, (Y(l), X(l)) represent the panel cycle series data for all series (or a vector of multiple cycle series data).
Given the panel time series data, (Y(t),X(t), reduce each multiple time series, (yi,t,{right arrow over (x)}i,t); to a reduced vector, {right arrow over (r)}i={ri,m}m=1M, of uniform length, M. Alternatively, given the panel cycle series data, (Y(l),X(l)), reduce each multiple cycle series, (yi,l,{right arrow over (x)}i,l), to a reduced data vector, {right arrow over (r)}i={ri,m}m=1M, of uniform length, M.
For example, features extracted from the ith multiple time series, (yi,t,{right arrow over (x)}i,t). The features may be the seasonal indices where M is the seasonality, or the features may be the cross-correlation analysis results where M is the number of time lags.
The resulting reduced data matrix, R={{right arrow over (r)}i}i=1N has uniform dimension (N×M). Uniform dimensions (coordinate form) are needed for many data mining techniques, such as computing distance measures and clustering data.
Given the panel time series data, (Y(t),X(t)), compare each multiple time series, (yi,t,{right arrow over (x)}i,t), using similarity measures. Alternatively, given the panel cycle series data, (Y(l),X(l)); compare each multiple cycle series, (yi,l,{right arrow over (x)}i,l), using a similarity measures.
Let si,j=Sim({right arrow over (y)}i,{right arrow over (y)}j) represent the similarity measure between the ith and jth series. Let {right arrow over (s)}i={si,j}j=1N represent the similarity vector of uniform length, N, for the ith series.
The resulting similarity matrix, S={{right arrow over (s)}i}i=1N has uniform dimension (N×N). Uniform dimensions (coordinate form) are needed for many data mining techniques, such as computing distance measures and clustering data.
Given the panel time series data, (Y(t),X(t)) compute the reduce data matrix, R={{right arrow over (r)}i}i=1N, and/or the similarity matrix, S={{right arrow over (s)}i}i=1N. Alternatively, given the panel cycle series data, (Y(l),X(l)) compute the reduce data matrix, R={{right arrow over (r)}i}i=1N, and/or the similarity matrix, S={{right arrow over (s)}i}i=1N.
A panel properties matrix can be formed by merging the rows of the reduce data matrix and the similarity matrix.
Let P=, S) represent the panel properties matrix of uniform dimension (N×(M+N)). Let {right arrow over (p)}i=({right arrow over (r)}i,{right arrow over (s)}i) represent the panel properties vector for the ith series of uniform dimension (1×(M+N)).
Given the panel properties vectors, {right arrow over (p)}i{pi,j}j=1M+N, of uniform length, M+N, let di,j=D({right arrow over (p)}i,{right arrow over (p)}j) represent the distance between the panel properties vectors associated with ith and jth series where D( ) represents the distance measure. Let {right arrow over (d)}i={di,j}j=1N be the distance vector associated with the ith series. Let D={{right arrow over (d)}i}i=1N be the distance matrix associated with all of the series.
Distance measures do not depend on time/season/cycle index nor do they depend on the reduction dimension, M. The dimensions of the distance matrix are (N×N).
If the distance between the Panel Properties Vectors is known, {right arrow over (p)}i these distances can be used as a surrogate for the distances between the Panel Series Vectors, (yi,t). In other words, {right arrow over (p)}i is close {right arrow over (p)}j to; then (yi,t) is close to (yj,t).
Let K represents the number of attributes recorded in the attribute data and let k=1, . . . , K represent the attribute index.
For example, K could represent the number of attributes associated with the products for sale in the marketplace and k could represent the kth attribute of the products.
There may be many attributes associated with a given time series. Some or all of the attributes may be useful in the analysis. In the following discussion, the attributes index, k=1, . . . , K, may represent all of the attributes or those attributes that are deemed important by the analyst.
Typically, the number of attribute variables is implicitly defined by the number of selected attributes.
Let ai,k represent the attribute data value for kth attribute associated with ith series. The attribute data values are categorical (ordinal, nominal) and continuous (interval, ratio). Let {right arrow over (a)}i={ai,k}k=1K represent the attribute data vector for the ith series where i=1, . . . , N. Let A={{right arrow over (a)}i}i=1N be the set of all possible attribute data vectors. Let Ak={ai,k}i=1N be the set of attribute values for the kth attribute for all the series.
For example, ai,k could represent consumer demographic, product distribution, price level, test market information, or other information for the ith product.
Analyzing the (discrete or continuous) distribution of an attribute variable values, Ak={ai,k}i=1N, can be useful for new product forecasting in determining the attribute values used to select the pool of candidate products to be used in the analysis. In general, a representative pool of candidate products that are similar to the new product is desired; however, a pool that is too large or too small is often undesirable. A large pool may be undesirable because the pool may not be homogeneous in nature. A small pool may be undesirable because it may not capture all of the potential properties and/or variation.
Let A={{right arrow over (a)}i}i=1N represent the attribute data set. In the following discussion, the attributes data set, A, may represent all of the attributes or those attributes that are deemed important to the analyses.
The attributes may not depend on the time/season/cycle index. In other words, they are time invariant. The analyst may choose from the set of the attributes and their attribute values for consideration. Sometimes the product attributes are textual in nature (product descriptions, sales brochures, and other textual formats). Text mining techniques may be used to extract the attribute information into formats usable for statistical analysis. Sometimes the product attributes are visual in nature (pictures, drawings, and other visual formats). This information may be difficult to use in statistical analysis but may be useful for judgmental analysis.
Let J represents the number of derived attributes computed from the time series data and let j=1, . . . , J represent the derived attribute index.
For example, J could represent the number of derived attributes associated with the historical time series data and j could represent the jth derived attribute.
There may be many derived attributes associated with the historical time series data set. Some or all of the derived attributes may be useful in the analysis. In the following discussion, the derived attributes index, j=1, . . . , J, may represent all of the derived attributes or those derived attributes that are deemed important by the analyst.
Typically, the number of derived attribute variables is implicitly defined by the number of selected derived attributes.
Let gi,j represent the derived attribute data value for jth derived attribute associated with ith series. The attribute data values are categorical (interval, ordinal, nominal). Let {right arrow over (g)}i={gi,j}j=1J represent the derived attribute data vector for the ith series where i=1, . . . , N. Let G={{right arrow over (g)}i}i=1N be the set of all possible derived attribute data vectors. Let Gj={gi,j}i=1N be the set of attribute values for the jth derived attribute for all the series.
For example, gi,j could represent a discrete-valued cluster assignment, continuous-valued price elasticity, continuous-valued similarity measure, or other information for the ith series.
Analyzing the (discrete or continuous) distribution of an derived attribute variable values, Gj={gi,j}i=1N, is useful for new product forecasting in determining the derived attribute values used to select the pool of candidate products to be used in the analysis. In general, a representative pool of candidate products that are similar to the new product is desired; however, a pool that is too large or too small is often undesirable. A large pool may be undesirable because the pool may not be homogeneous in nature. A small pool may be undesirable because it may not capture all of the potential properties and/or variation.
Let G={{right arrow over (g)}i}i=1N represent the derived attribute data set. In the following discussion, the derived attributes data set, G, may represent all of the derived attributes or those derived attributes that are deemed important to the analyses. The derived attributes may not depend on the time/season/cycle index. In other words, they may be time invariant. However, the means by which they are computed may depend on time. The analyst may choose from the set of the derived attributes and their derived attribute values for consideration.
Certain computations may be made by a time series exploration system. The following describes certain of those computations. For example, given a panel series data set, the series can be summarized to better understand the series global properties.
Given a time series, yi,t, or cycle series, yi,l, summarizes the time series using descriptive statistics. Typically, the descriptive statistics are vector-to-scalar data reductions and have the form: αi=UnivariateDescrtiveStatistic({right arrow over (y)}i)
For example:
missing values are ignored in the summation
missing values are ignored in the summation
missing values are ignored in the minimization
Maximum,
missing values are ignored in the maximization
Time series descriptive statistics can be computed for each independent time series vector.
Given a panel time series, Y(t), or panel cycle series, Y(t)=Y(i), summarize the panel series using descriptive statistics. Essentially, the vector series descriptive statistics summarize the univariate descriptive statistics. Typically, the vector descriptive statistics are matrix-to-scalar data reductions and have the form: α=VectorDescriptiveStatistic(Y(t))
Following are some examples:
missing values are ignored in the minimization
missing values are ignored in the maximization
Likewise, vector series descriptive statistics can be computed for each independent time series vector.
Certain transformations may be performed by a time series exploration system. The following describes certain example time series transformations.
Given a panel series data set, the series can be transformed to another series which permits a greater understanding of the series properties over time.
Given a time series, yi,t or cycle series, yi,l, univariately transform the time series using a univariate time series transformation. Typically, univariate transformations are vector-to-vector (or series-to-series) operations and have the form: {right arrow over (z)}i=UnivariateTransform({right arrow over (y)}i)
Following are some examples:
Given a dependent time series, yi,t, or cycle series, yi,l, and an independent time series, xi,t, multivariately transform the time series using a multiple time series transformation. Typically, multiple time series transforms are matrix-to-vector operations and have the form:
{right arrow over (z)}i=MultipleTransforms({right arrow over (y)}i,{right arrow over (x)}i)
For example:
Given a panel time series, yi,t, or panel cycle series, yi,t=yi,l, multivariately transform the panel series using a vector series transformation. Typically, the vector transformations are matrix-to-matrix (panel-to-panel) operations and have the form: Z=VectorTransform(Y)
Many vector transformations are just univariate transformations applied to each series individually. For each series index
{right arrow over (z)}
i=UnivariateTransform({right arrow over (y)}i)i=1, . . . , N
Some vector transformations are applied to a vector series jointly.
For example:
Certain time series data reduction operations may be performed by a time series exploration system. Data mining techniques include clustering, classification, decision trees, and others. These analytical techniques are applied to large data sets whose observation vectors are relatively small in dimension when compared to the length of a transaction series or time series.
In order to effectively apply these data mining techniques to a large number of series, the dimension of each series can be reduced to a small number of statistics that capture their descriptive properties. Various transactional and time series analysis techniques (possibly in combination) can be used to capture these descriptive properties for each time series.
Many transactional and time series databases store the data in longitudinal form, whereas many data mining software packages utilize the data in coordinate form. Dimension reduction extracts important features of the longitudinal dimension of the series and stores the reduced sequence in coordinate form of fixed dimension. Assume that there are N series with lengths {T1, . . . , TN}.
In longitudinal form, each variable (or column) represents a single series, and each variable observation (or row) represents the series value recorded at a particular time. Notice that the length of each series, Ti, can vary.
{right arrow over (y)}
i
={y
i,t}t=1T
where {right arrow over (y)}i is (Ti×1). This form is convenient for time series analysis but less desirable for data mining
In coordinate form, each observation (or row) represents a single reduced sequence, and each variable (or column) represents the reduced sequence value. Notice that the length of each reduced sequence, M, is fixed.
{right arrow over (r)}
i
={r
i,m}m=1M for i=1, . . . , N
where {right arrow over (r)}i is (1×M). This form is convenient for data mining but less desirable for time series analysis.
To reduce a single series, a univariate reduction transformation maps the varying longitudinal dimension to the fixed coordinate dimension.
{right arrow over (r)}
i=Reducei({right arrow over (y)}i) for i=1, . . . , N
where {right arrow over (r)}i is (1×M), Yi is (Ti×1), and Reducei( ) is the reduction transformation (e.g., seasonal decomposition).
For multiple series reduction, more than one series is reduced to a single reduction sequence. The bivariate case is illustrated.
{right arrow over (r)}
i=Reducei({right arrow over (y)}i,{right arrow over (x)}i,k) for i=1, . . . , N
where {right arrow over (r)}i is (1×M), {right arrow over (y)}i is (Ti×1), {right arrow over (x)}i,k is (Ti×1), and Reducei( ) is the reduction transformation (e.g., cross-correlations).
In the above discussion, the reduction transformation, Reducei( ), is indexed by the series index, i=1, . . . , N, but typically it does not vary and further discussion assumes it to be the same, that is, Reduce( )=Reducei( ).
Given a time series, yi,t, or cycle series, yi,l, univariately reduce the time series using a time series data reduction. Typically, univariate reductions are vector-to-vector operations and have the form: {right arrow over (r)}i=UnivariateReduction({right arrow over (y)}i)
Following are some examples:
{right arrow over (r)}
i=MultipleReduction({right arrow over (y)}i,{right arrow over (x)}i)
For example,
Given a panel time series, yi,t, or panel cycle series, yi,t=yi,l, multivariately reduce the panel series using a vector series reduction. Typically, the vector reductions are matrix-to-matrix operations and have the form: R=Vector Reduction(Y)
Many vector reductions include univariate reductions applied to each series individually. For each series index
{right arrow over (r)}
i=UnivariateReduction({right arrow over (y)}i)i=1, . . . , N
Some vector reductions are applied to a vector series jointly.
For example:
Given a time series, yi,t, or cycle series, yi,l, derive an attribute using a univariate time series computation. Typically, univariate attribute derivations are vector-to-scalar operations and have the form: gi,j=UnivariateDerivedAttribute({right arrow over (y)}i)
For example:
Given a dependent time series, yi,t, or cycle series, yi,l, and an independent time series, xi,t, derive an attribute using a multiple time series computation. Typically, multiple attribute derivations are matrix-to-scalar operations and have the form:
g
i,j=MultipleDerivedAttribute({right arrow over (y)}i,{right arrow over (x)}i)
Following are some examples:
Given a panel time series, Y(t), or panel cycle series, Y(t)=Y(l), compute a derived attribute values vector associated with the panel series. Essentially, the vector attribute derivation summarizes or groups the panel time series. Typically, the vector series attribute derivations are matrix-to-vector operations and have the form:
G
j=VectorDerivedAttribute(Y(t))
Many vector series attribute derivations are just univariate or multiple attribute derivation applied to each series individually. For each series indices,
g
i,j=UnivariateDerivedAttribute({right arrow over (y)}i)i=1, . . . ,N
OR
g
i,j=MultipleDerivedAttribute({right arrow over (y)}i,{right arrow over (x)}i)i=1, . . . ,N
Some vector series attribute derivations are applied to a vector series jointly.
For example:
Data provided to, utilized by, and outputted by a time series exploration system may be structured in a variety of forms. The following describes concepts related to the storage and representation of the time series data.
Table 1 describes the storage of the Panel Series Data.
Table 1 represents a panel series. Each shaded area of the table represents a multiple time series. Each analysis variable column in each shaded area of the table represents a univariate time series. Each analysis variable column represents a vector time series.
The amount of data associated with a Panel Series may be quite large. The Panel Series may be represented efficiently in memory (e.g., only one copy of the data in memory is stored). The Panel Series, (Y(t),X(t)), contains several multiple series data, (yi,t,{right arrow over (x)}i,t), which contains a fixed number univariate series data, yi,t or {right arrow over (x)}i,t. The independent variables are the same for all dependent series though some may contain only missing values.
The data set associated with a Panel Series may be quite large. It may be desirable to read the data set only once. The user may be warned if the data set is to be reread.
Reading/writing the Panel Series Data into/out of memory may be performed as follows:
For each Multiple Time Series (or by group), read/write all of the Univariate Time Series associated with the by group. Read/write yi,t or {right arrow over (x)}i,t to form (yi,t,{right arrow over (x)}i,t) for each by group. Read/write each by group (yi,t,{right arrow over (x)}i,t) to form (Y(t),X(t)).
A time series exploration may store and manipulate attribute data
Table 2 describes example storage of Attribute Data.
Table 2 represents an attribute data set, A={{right arrow over (a)}i}i=1N. Each shaded row of the table represents an attribute vector for single time series, {right arrow over (a)}i={{right arrow over (a)}i,k}k=1K. Each attribute variable column represents an attribute value vector across all time series, Ak={{right arrow over (a)}i,k}l=1N. Each table cell represents a single attribute value, ai,k.
Table 2 describes the shaded areas of following Table 3 associated with the Panel Series.
Notice that the Panel Series has a time dimension but the Attributes do not. Typically, the attribute data set is much smaller than the panel series data set. Table 3 show that the series index, i=1, . . . , N, are a one-to-one mapping between the tables. The mapping is unique but there may be time series data with no associated attributes (missing attributes) and attribute data with no time series data (missing time series data).
The amount of data associated with the attributes may be quite large. The Attribute Data may be represented efficiently in memory (e.g., only one copy of the data in memory is stored). The attribute data, A={{right arrow over (a)}i}i=1N, contains several attribute value vectors, Ak={{right arrow over (a)}i,k}i=1N, which contains a fixed number attribute values, ai,k, for discrete data and a range of values for continuous data. The attribute variables are the same for all time series.
The data set associated with Attributes may be quite large. It may be desirable to only read data once if possible. The user may be warned if the data set is to be reread.
Reading/writing attribute data into/out of memory can be performed as follows:
For each attribute vector (or by group), read/write all of the attribute values associated with the by group.
In some implementations it may be desirable to limit or reduce an amount of data stored. The following discussion describes some practical concepts related to the storage and representation of the reduced data.
Table 4 represents a reduced data set, R={{right arrow over (r)}i}i=1N. Each shaded row of the table represents a reduced data vector for single time series, {right arrow over (r)}i={{right arrow over (r)}i,m}m=1M. Each reduced variable column represents a reduced value vector across all time series, Rm={{right arrow over (r)}i,m}l=1N. Each table cell represents a single reduced value, ri,m.
Table 5 describes the shaded areas of the following table associated with the Panel Series.
Notice that the Panel Series has a time dimension but the Reduced Data do not. Sometimes, the reduced data set is much smaller than the panel series data set. Tables 4 and 5 show that the series index, i=1, . . . , N, are a one-to-one mapping between the tables. The mapping is unique but there may be time series data with no associated reduced data (missing attributes) and reduced data with no time series data (missing time series data).
Dimension reduction may transform the series table (T×N) to the reduced table (N×M) where T=max{T1, . . . , TN} and where typically M<T. The number of series, N, can be quite large; therefore, even a simple reduction transform may manipulate a large amount of data. Hence, it is important to get the data in the proper format to avoid the post-processing of large data sets.
Time series analysts may often desire to analyze the reduced table set in longitudinal form, whereas data miners often may desire analyze the reduced data set in coordinate form.
Transposing a large table from longitudinal form to coordinate form and vice-versa form can be computationally expensive.
In some implementations a time series exploration system may make certain distance computations. The following discussion describes some practical concepts related to the storage and representation of the distance.
Table 6 describes the storage of the Distance.
Table 6 represents a distance matrix data set, D={{right arrow over (d)}i}i=1N. Each shaded row of the table represents a distance vector for single time series, {right arrow over (d)}i={di,j}j=1N. Each distance variable column represents a distance measure vector across all time series, Dj={di,j}i=1N. Each table cell represents a single distance measure value, di,j.
Table 7 describes the shaded areas of the following table associated with the Panel Series.
Notice that the Panel Series has a time dimension but the Distance Matrix does not. Typically, the distance matrix data set is much smaller than the panel series data set.
Table 7 shows that the series index, i=1, . . . , N, are a one-to-one mapping between the tables. The mapping is unique but there may be time series data with no associated distance measures (missing measures) and distance measures without time series data (missing time series data).
In some implementations a time series exploration system may store derived data. The following discussion describes some practical concepts related to the storage and representation of the attribute data.
Table 8 describes storage of the derived attribute data.
Table 8 represents a derived attribute data set, G={{right arrow over (g)}i}i=1N. Each shaded row of the table represents a derived attribute vector for single time series, Gj={gi,j}i=1N. Each attribute variable column represents a derived attribute value vector across all time series, Gj={gi,j}i=1N. Each table cell represents a single derived attribute value, gi,j.
The amount of data associated with the derived attributes may be quite large. The derived attribute data may be represented efficiently in memory (e.g., only one copy of the data in memory is stored).
The derived attribute data, G={{right arrow over (g)}i}i=1N, contains several derived attribute value vectors, Gj={gi,j}i=1N, which contains a fixed number derived attribute values, gi,j, for discrete data and a range of values for continuous data. The derived attribute variables are the same for all time series.
The data set associated with Derived Attributes may be quite large. It may be desirable to only read data once if possible. The user may be warned if the data set is to be reread.
Reading/writing derived attribute data into/out of memory may be performed as follows:
For each Derived Attribute Vector (or by group), read/write all of the derived attribute values associated with the by group.
A disk controller 2660 interfaces one or more optional disk drives to the system bus 2652. These disk drives may be external or internal floppy disk drives such as 2662, external or internal CD-ROM, CD-R, CD-RW or DVD drives such as 2664, or external or internal hard drives 2666. As indicated previously, these various disk drives and disk controllers are optional devices.
Each of the element managers, real-time data buffer, conveyors, file input processor, database index shared access memory loader, reference data buffer and data managers may include a software application stored in one or more of the disk drives connected to the disk controller 2660, the ROM 2656 and/or the RAM 2658. Preferably, the processor 2654 may access each component as required.
A display interface 2668 may permit information from the bus 2652 to be displayed on a display 2670 in audio, graphic, or alphanumeric format. Communication with external devices may optionally occur using various communication ports 2672.
In addition to the standard computer-type components, the hardware may also include data input devices, such as a keyboard 2673, or other input device 2674, such as a microphone, remote control, pointer, mouse and/or joystick.
Additionally, the methods and systems described herein may be implemented on many different types of processing devices by program code comprising program instructions that are executable by the device processing subsystem. The software program instructions may include source code, object code, machine code, or any other stored data that is operable to cause a processing system to perform the methods and operations described herein and may be provided in any suitable language such as C, C++, JAVA, for example, or any other suitable programming language. Other implementations may also be used, however, such as firmware or even appropriately designed hardware configured to carry out the methods and systems described herein.
The systems' and methods' data (e.g., associations, mappings, data input, data output, intermediate data results, final data results, etc.) may be stored and implemented in one or more different types of computer-implemented data stores, such as different types of storage devices and programming constructs (e.g., RAM, ROM, Flash memory, flat files, databases, programming data structures, programming variables, IF-THEN (or similar type) statement constructs, etc.). It is noted that data structures describe formats for use in organizing and storing data in databases, programs, memory, or other computer-readable media for use by a computer program.
The computer components, software modules, functions, data stores and data structures described herein may be connected directly or indirectly to each other in order to allow the flow of data needed for their operations. It is also noted that a module or processor includes but is not limited to a unit of code that performs a software operation, and can be implemented for example as a subroutine unit of code, or as a software function unit of code, or as an object (as in an object-oriented paradigm), or as an applet, or in a computer script language, or as another type of computer code. The software components and/or functionality may be located on a single computer or distributed across multiple computers depending upon the situation at hand.
It should be understood that as used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. Further, as used in the description herein and throughout the claims that follow, the meaning of “each” does not require “each and every” unless the context clearly dictates otherwise. Finally, as used in the description herein and throughout the claims that follow, the meanings of “and” and “or” include both the conjunctive and disjunctive and may be used interchangeably unless the context expressly dictates otherwise; the phrase “exclusive or” may be used to indicate situation where only the disjunctive meaning may apply.
This application is a Continuation of U.S. patent application Ser. No. 13/548,307, filed Jul. 13, 2012, entitled “COMPUTER-IMPLEMENTED SYSTEMS AND METHODS FOR TIME SERIES EXPLORATION”, which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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Parent | 13548307 | Jul 2012 | US |
Child | 14736131 | US |