Stack Table Variables

Combine values from multiple table variables into one table variable in the Live Editor

Description

The Stack Table Variables task enables you to interactively stack values from multiple table or timetable variables into one variable. The task automatically generates MATLAB^® code for your live script. The generated code uses the stack function.

To stack variables means to interleave values from specified variables into one variable of the output. Stacking also adds an indicator variable to the output. In each row of the output, the value of the indicator variable indicates which variable of the input provided the data. The diagram shows the result of stacking a table.

Open the Task

To add the Stack Table Variables task to a live script in the MATLAB Editor:

• On the Live Editor tab, select Task > Stack Table Variables.

• Or, in a code block in the script, type a relevant keyword, such as stack. Select Stack Table Variables from the suggested command completions.

Examples

Stack Table Variables Using Live Editor Task

This example shows how to stack variables by using the Stack Table Variables Live Editor task. It takes values from multiple variables in an input table, and combines them into one variable in an output table.

First, load a table from a sample file that lists the number of power company customers who experienced electric power outages. The sample data are aggregated by month. The power company serves three regions in the United States. So there are three variables, NorthEast, MidWest, and SouthEast, that list the numbers of customers affected in each region.

load customersByRegion.mat
customersByRegion

customersByRegion=6×4 table
        Month        NorthEast    MidWest    SouthEast
    _____________    _________    _______    _________

     October-2023       3492         565       1027   
    November-2023       2944        1293        834   
    December-2023       2559         936       1412   
     January-2024      12045       50117          0   
    February-2024       4931        1089        137   
       March-2024       3018         942        870   

Stack the customer outage data so that the numbers from the NorthEast, MidWest, and SouthEast variables are in one variable in the output table.

Add the Stack Table Variables task to your live script.

• To copy values from the Month variable to rows of the output table, select Constant from the drop-down list above it in the task.

• To combine the values from the NorthEast, MidWest, and SouthEast variables by stacking them into one variable of the output, select Stack for each variable.

The name of the stacked variable in the output comes from combining the input variable names.

The task also stacks the names of the input variables into a new variable, named NorthEast_MidWest_SouthEast_Indicator, that indicates the regions for the customer outage data.

stackedTable=18×3 table
        Month        NorthEast_MidWest_SouthEast_Indicator    NorthEast_MidWest_SouthEast
    _____________    _____________________________________    ___________________________

     October-2023                  NorthEast                              3492           
     October-2023                  MidWest                                 565           
     October-2023                  SouthEast                              1027           
    November-2023                  NorthEast                              2944           
    November-2023                  MidWest                                1293           
    November-2023                  SouthEast                               834           
    December-2023                  NorthEast                              2559           
    December-2023                  MidWest                                 936           
    December-2023                  SouthEast                              1412           
     January-2024                  NorthEast                             12045           
     January-2024                  MidWest                               50117           
     January-2024                  SouthEast                                 0           
    February-2024                  NorthEast                              4931           
    February-2024                  MidWest                                1089           
    February-2024                  SouthEast                               137           
       March-2024                  NorthEast                              3018           
      ⋮

Give the variables of the output table more meaningful names. To rename table variables, use the renamevars function.

customersOutage = renamevars(stackedTable, ...
                             ["NorthEast_MidWest_SouthEast_Indicator" "NorthEast_MidWest_SouthEast"], ...
                             ["Region" "CustomersOutage"])

customersOutage=18×3 table
        Month         Region      CustomersOutage
    _____________    _________    _______________

     October-2023    NorthEast          3492     
     October-2023    MidWest             565     
     October-2023    SouthEast          1027     
    November-2023    NorthEast          2944     
    November-2023    MidWest            1293     
    November-2023    SouthEast           834     
    December-2023    NorthEast          2559     
    December-2023    MidWest             936     
    December-2023    SouthEast          1412     
     January-2024    NorthEast         12045     
     January-2024    MidWest           50117     
     January-2024    SouthEast             0     
    February-2024    NorthEast          4931     
    February-2024    MidWest            1089     
    February-2024    SouthEast           137     
       March-2024    NorthEast          3018     
      ⋮

Related Examples

• Add Interactive Tasks to a Live Script

Parameters

Input table — Names of table or timetable

drop-down list items

Specify the name of the input table or timetable timetables from the lists of all the nonempty tables and timetables that are in the workspace.

Variables to stack — Actions for input variables

drop-down list items

Specify the action to take for each variable in the input table or timetable. When stacking variables, there are three possible actions:

• Constant — Copy the variable to the output table or timetable. Replicate its values where needed in rows of the output.

• Stack — Stack the values from the variable into one variable of the output. For example, if you choose to stack three variables, all their values go into one variable of the output.

• Discard — Exclude the variable and its values from the output.

Version History

Introduced in R2020a

R2022a: Live Editor task does not run automatically if inputs have more than 1 million elements

This Live Editor task does not run automatically if the inputs have more than 1 million elements. In previous releases, the task always ran automatically for inputs of any size. If the inputs have a large number of elements, then the code generated by this task can take a noticeable amount of time to run (more than a few seconds).

When a task does not run automatically, the Autorun indicator is disabled. You can either run the task manually when needed or choose to enable the task to run automatically.