filter a timetable by day

Hi!

How can I create timetable that only groups the information from the following timetable by day?

timeStamps = datetime([2017 3 4; 2017 3 5; 2017 3 4; 2017 3 5; 2017 3 4; 2017 3 5; 2017 3 4; 2017 3 5]);

hour = [8 8 8 8 9 9 9 9]';


Volume = [5 10 15 20 25 30 35 40]';

Price= [40 35 30 25 20 15 10 5]';

T= table(timeStamps, hour, Volume, Price)
TT= table2timetable(T)

This is just an example, my real timetable is composed of several days, perhaps with a for loop?

Answer 1

[Star Strider]

I am not certain what you intend by ‘groups’.

One option is to use the retime function:

TTRT = retime(TT, 'daily','mean')

producing:

TTRT =

  2×3 timetable

    timeStamps     hour    Volume    Price
    ___________    ____    ______    _____

    04-Mar-2017    8.5       20       25  
    05-Mar-2017    8.5       25       20  

[Angelavtc]

Thank you @star Strider, what I want is to divide my table by days, to create daily subtables. I dont need to do any other calculation (like the mean). I want to have a fast way of doing it as I have a dataset composed by several years, months, and of course, a lot of repeated daily observations to group. So for this small example, I will need to create 2 subtables (one for 04-Mar-2017 and the other for 05-Mar-2017) with their corresponding hour, Price and Volume observations. Thanks in advance!

[Steven Lord]

Index into your timetable using a timerange.

tr  = timerange(datetime('today'), 'day')

[Star Strider]

To create separate tables from ‘TT’:

G = findgroups(TT.timeStamps);
TTS = accumarray(G, (1:size(TT,1)).', [], @(x){TT(x,:)});

producing:

TTS_1 = TTS{1}

TTS_1 =

  4×3 timetable

    timeStamps     hour    Volume    Price
    ___________    ____    ______    _____

    04-Mar-2017     8         5       40  
    04-Mar-2017     8        15       30  
    04-Mar-2017     9        25       20  
    04-Mar-2017     9        35       10

[Angelavtc]

woow @Star Strider, this works perfect! Amazing! Merci!

[Angelavtc]

@Star Strider but how can I do a loop so it creates the daily subtimetables from one command. For example here, something like:

for i=1:length(TTS);
    TTS_i=TTS{i};
end

[Star Strider]

As always, my pleasure!

My code creates them automatically. Use the addressing I used to see and use each one.