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 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.

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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 or timetable. Select Retime Timetable from the suggested command completions.

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);

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.

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

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.

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

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 icon is disabled.

• To run a task manually, on the Live Editor tab, click the Run Section button.

• To enable running the section automatically, click the Autorun icon. The icon updates to display the enabled state.

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.