Retime Timetable

Resample or aggregate timetable data in the Live Editor

Description

The Retime Timetable task lets you interactively change the row times of a timetable and then resample or aggregate the data in its variables. The task also automatically generates MATLAB^® code for your live script.

Using this task, you can:

• Interpolate data values at new row times.

• Aggregate data into time bins (for example, to create a timetable containing quarterly means from monthly data).

• Remove rows that have duplicate row times.

• Make an irregular timetable into a regular one by specifying a uniform time step or sample rate.

For more information on Live Editor tasks, see Add Interactive Tasks to a Live Script.

Related Functions

Retime Timetable generates code that uses the retime function.

Open the Task

To add the Retime Timetable task to a live script in the MATLAB Editor:

• On the Live Editor tab, select Task > Retime Timetable.

• In a code block in the script, type a relevant keyword, such as retime, timetable, upsample, or downsample. Select Retime Timetable from the suggested command completions. For some keywords, the task automatically updates one or more corresponding parameters.

Examples

Resample and Aggregate Timetable Data Using Live Editor Task

The example shows how to resample and aggregate data in a timetable by using the Retime Timetable Live Editor task. You also can apply different rules for adjusting timetable variables in different ways.

Resample Data

Create a timetable using column vectors of data. The row times are between 10 and 50 milliseconds.

Intensity = [100 98.7 95.2 101.4 99.1]';
Time = milliseconds([11 20 34 40.3 49.9])';
TT1 = timetable(Time,Intensity)

TT1=5×1 timetable
       Time       Intensity
    __________    _________

    0.011 sec         100  
    0.02 sec         98.7  
    0.034 sec        95.2  
    0.0403 sec      101.4  
    0.0499 sec       99.1  

Add the Retime Timetable task to your live script. Resample the data in TT.

• To specify a sample rate of 100 Hz, use the Selection method menus.

• To adjust the data in the Intensity variable by using linear interpolation, use the General rule menu.

newTimetable=5×1 timetable
      Time      Intensity
    ________    _________

    0.01 sec     100.14  
    0.02 sec       98.7  
    0.03 sec       96.2  
    0.04 sec      101.1  
    0.05 sec     99.076  

Aggregate Data

Load a second timetable from the bostonTT MAT-file. This timetable has temperature, wind speed, and rainfall measurements for the city of Boston. The measurements are approximately six hours apart but are irregular.

load bostonTT
Boston

Boston=6×3 timetable
           Time            Temp    WindSpeed    Rain
    ___________________    ____    _________    ____

    2016-06-09 06:03:00    59.5       0.1       0.05
    2016-06-09 12:00:23      63       2.3       0.08
    2016-06-09 18:02:57    61.7       3.1       0.13
    2016-06-10 06:01:47    55.4       5.7       0.15
    2016-06-10 12:06:00    62.3       2.6       0.87
    2016-06-10 18:02:57    58.8       6.2       0.33

Add a second instance of the Retime Timetable task to your live script. Aggregate the data into daily time bins.

• To specify a time step of one day, use the Selection method menus.

• To calculate means of the timetable variables, use the General rule menu.

• To specify a different rule for the Rain variable, use the Exceptions menus. Add an exception to interpolate rainfall measurements at the beginning of each day.

newTimetable2=2×3 timetable
           Time             Temp     WindSpeed      Rain  
    ___________________    ______    _________    ________

    2016-06-09 00:00:00      61.4     1.8333      0.019529
    2016-06-10 00:00:00    58.833     4.8333       0.13993

Related Examples

• Add Interactive Tasks to a Live Script
• Clean Timetable with Missing, Duplicate, or Nonuniform Times
• Resample and Aggregate Data in Timetable
• Combine Timetables and Synchronize Their Data
• Retime and Synchronize Timetable Variables Using Different Methods

Parameters

Input timetable — Name of timetable

drop-down list item

Specify the name from a list of all the nonempty timetables that are in the workspace.

Selection method — Method for specifying row times

drop-down list item

Specify the method for calculating new row times of the timetable.

• Time step — Length of time between consecutive regularly spaced row times.

• Sample rate — Sample rate or frequency for regularly spaced row times.

• Times from workspace — Workspace variable that is a vector of datetime or duration values. The times in the vector replace the row times of the timetable. The times need not be regularly spaced.

General rule — Rule for adjusting data values

drop-down list item

Specify the rule for adjusting data values in the variables of the timetable. The rule applies to all variables unless exceptions are specified. You can resample or aggregate data values to:

• Fill gaps with missing data indicators or a constant value.

• Interpolate data values to the new row times. For example, resample data measured at 100 Hz to 200 Hz.

• Aggregate data into time bins. For example, calculate a daily mean from data values measured at every hour.

Exceptions — Different rule or rules for adjusting specified variables

drop-down list item

Click the Add button. Then specify a timetable variable from the drop-down list of variable names that appears.

• To adjust the data in the specified variable, select a rule from the drop-down list of rules to the right of the variable name. The rule for the exception can differ from the general rule.

• To specify exceptions for other timetable variables, click the + button to the right of the first exception. New drop-down lists of variable names and rules appear below the previous exception.

Version History

Introduced in R2020a

R2024b: Specify custom function as local function or function handle

When you select the Custom function option for the General rule method, you can either select a locally defined function or specify a function handle.

To select a local function:

1. Select Custom function.

2. Select Local function from the next menu.

3. If you want to add a new local function to the script, click New. The task generates template code for a custom aggregation function within the live script. To customize this code, edit it in the live script.

4. Select the name of the local function from the select menu.

To specify a function handle:

1. Select Custom function.

2. Select Function handle from the next menu.

3. Specify a function handle in the text box.

   You can specify a handle to a MATLAB function or write an anonymous function in the text box. For example, to specify mean as the function, type @mean in the text box.

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.

R2020b: Retime Timetable Live Editor Task: Use linear interpolation as default general rule for adjusting data

In R2020b, linear interpolation is the default general rule for adjusting data in the Retime Timetable live editor task. In previous releases, the default general rule was to fill gaps in the output timetable with missing values.

However, even in R2020b the default rule reverts to filling gaps with missing values if either of these conditions is met:

• The row times of the input timetable are not sorted.

• The input timetable has at least one variable whose data type is not numeric, datetime, or duration.