compact

Reduce size of direct forecasting model

Since R2023b

Syntax

CompactMdl = compact(Mdl)

Description

CompactMdl = compact(Mdl) returns a compact model (compactMdl), the compact version of the trained direct forecasting model Mdl.

CompactMdl does not contain the training data, whereas Mdl contains the training data in its X and Y properties. Therefore, although you can predict and forecast using CompactMdl, you cannot perform tasks such as cross-validation with the compact model.

Examples

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Reduce Size of Direct Forecasting Model

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Reduce the size of a full direct forecasting model by removing the training data from the model. You can use a compact model to improve memory efficiency.

Load the sample file TemperatureData.csv, which contains average daily temperatures from January 2015 through July 2016. Read the file into a table. Observe the first eight observations in the table.

temperatures = readtable("TemperatureData.csv");
head(temperatures)

    Year       Month       Day    TemperatureF
    ____    ___________    ___    ____________

    2015    {'January'}     1          23     
    2015    {'January'}     2          31     
    2015    {'January'}     3          25     
    2015    {'January'}     4          39     
    2015    {'January'}     5          29     
    2015    {'January'}     6          12     
    2015    {'January'}     7          10     
    2015    {'January'}     8           4

For this example, use a subset of the temperature data that omits the first 100 observations.

Tbl = temperatures(101:end,:);

Create a datetime variable t that contains the year, month, and day information for each observation in Tbl. Then, use t to convert Tbl into a timetable.

numericMonth = month(datetime(Tbl.Month, ...
    InputFormat="MMMM",Locale="en_US"));
t = datetime(Tbl.Year,numericMonth,Tbl.Day);
Tbl.Time = t;
Tbl = table2timetable(Tbl);

Plot the temperature values in Tbl over time.

plot(Tbl.Time,Tbl.TemperatureF)
xlabel("Date")
ylabel("Temperature in Fahrenheit")

Create a full direct forecasting model by using the data in Tbl. Train the model using a decision tree learner. All three of the predictors (Year, Month, and Day) are leading predictors because their future values are known. To create new predictors by shifting the leading predictor and response variables backward in time, specify the leading predictor lags and the response variable lags.

Mdl = directforecaster(Tbl,"TemperatureF", ...
    Learner="tree", ...
    LeadingPredictors="all",LeadingPredictorLags={0:1,0:1,0:7}, ...
    ResponseLags=1:7)

Mdl = 
  DirectForecaster

                  Horizon: 1
             ResponseLags: [1 2 3 4 5 6 7]
        LeadingPredictors: [1 2 3]
     LeadingPredictorLags: {[0 1]  [0 1]  [0 1 2 3 4 5 6 7]}
             ResponseName: 'TemperatureF'
           PredictorNames: {'Year'  'Month'  'Day'}
    CategoricalPredictors: [2]
                 Learners: {[1x1 classreg.learning.regr.CompactRegressionTree]}
                   MaxLag: [7]
          NumObservations: [465]

Mdl is a DirectForecaster object. By default, the horizon is one step ahead. That is, Mdl predicts a value that is one step into the future.

Reduce the size of the model by using the compact object function.

compactMdl = compact(Mdl)

compactMdl = 
  CompactDirectForecaster

                  Horizon: 1
             ResponseLags: [1 2 3 4 5 6 7]
        LeadingPredictors: [1 2 3]
     LeadingPredictorLags: {[0 1]  [0 1]  [0 1 2 3 4 5 6 7]}
             ResponseName: 'TemperatureF'
           PredictorNames: {'Year'  'Month'  'Day'}
    CategoricalPredictors: [2]
                 Learners: {[1x1 classreg.learning.regr.CompactRegressionTree]}
                   MaxLag: [7]

compactMdl is a CompactDirectForecaster model object. compactMdl contains fewer properties than the full model Mdl.

Display the amount of memory used by each direct forecasting model.

whos("Mdl","compactMdl")

  Name            Size             Bytes  Class                                            Attributes

  Mdl             1x1             110401  timeseries.forecaster.DirectForecaster                     
  compactMdl      1x1              42541  timeseries.forecaster.CompactDirectForecaster

The full model is larger than the compact model.