Would be possible to calculate half hour average by using retime?

Hello,

The current time steps allowed in retime https://www.mathworks.com/help/matlab/ref/retime.html are:

 'yearly' One year
 'quarterly' One quarter
 'monthly' One month
 'weekly' One week
 'daily' One day
 'hourly' One hour
 'minutely' One minute
 'secondly' One second

But would be possible to calculate half hour average? or other specific time step average (like 5, 10, 15 minutes...) beside the standard here mentioned?

Thanks.

Answer 1

[Teja Muppirala]

Yes, there is an example a little bit down the in the documentation for RETIME , under this heading:

Interpolate Timetable Data to Arbitrary Times

I've copied the relevant sample code here:

%%Make sample data
Time = datetime({'2015-12-18 07:29:53';'2015-12-18 08:00:00';...
                 '2015-12-18 08:31:02';'2015-12-18 09:30:00'});
Temp = [37.3;41.9;45.7;39.8];
Pressure = [30.1;29.9;30.03;29.8];
TT1 = timetable(Time,Temp,Pressure)

%%Retime to 30 minute intervals
newTimes = [datetime('2015-12-18 07:30:00'):minutes(30):datetime('2015-12-18 09:30:00')];
TT2 = retime(TT1,newTimes,'linear')

[Teja Muppirala]

This example concerns interpolation, but aggregation works as well (for example, change 'linear' to 'mean').

[Peter Perkins]

Teja is correct. Just to expand a bit, those strings like 'yearly', 'quarterly', etc. are just conveniences for common uses. You can synchronize to any time vector you want as long as it's increasing. Doesn't even have to be regular.

[Robert]

Thank you, very appreciated Teja and Peter!

[Peter Perkins]

Update: In R2018a, there's a new syntax that makes this a bit easier:

tt = retime(tt,'regular',method,'TimeStep',minutes(30))

Answer 2

[Ohad Zivan]

From Matlab: Adjust Timetable Data to Regular Times Calculate the means over six-hour time intervals. Specify a regular time step using the 'regular' input argument and the 'TimeStep' name-value pair argument.

TT = retime(outdoors,'regular','mean','TimeStep',hours(6)); TT(1:5,:) ans=5×3 timetable Time Humidity TemperatureF PressureHg _________________ ______ __________ ________

    2015-11-15 00:00:00       48.9         51.45          29.61  
    2015-11-15 06:00:00       48.9         51.45           29.6  
    2015-11-15 12:00:00     49.025         51.45          29.61  
    2015-11-15 18:00:00       48.9        51.225         29.607  
    2015-11-16 00:00:00       48.5          51.4          29.61

you could do this example for minutes (30). much easier. https://www.mathworks.com/help/matlab/matlab_prog/resample-and-aggregate-data-in-timetable.html

[sm fattah]

thanks. It helped.