Create table from an other table

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Thomas Vescovini 2019-7-12

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https://ww2.mathworks.cn/matlabcentral/answers/471446-create-table-from-an-other-table

评论： Thomas Vescovini 2019-7-16

Maghreb0218.mat

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Hello everyone,

I created 33 tables containing 3 row with date (from 2002 to 2018 with day and month) and longitude, lattitude with the following code :

T = readtable('SouthernAfrica_0810.csv');
T.acq_date = datetime(T.acq_date,'F','dd/MM/uuuu');
SouthernAfrica_0810 = [T(:,6), T(:,1:2)];
save SouthernAfrica_0810.mat SouthernAfrica_0810

I would like to create tables representing the same thing for each month of each years wich make around 3000 tables (I need it to plot maps of fire pixels) but I'm not really feeling like doing it one by one...

Does anyone have an idea how to automatize the creation of those monthly tables for one the main table (I have linked one of the table in this message) ?

Thanks you, have a good day,

Thomas V.

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Peter Perkins 2019-7-15

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If you are just making one plot, the simplest thing is to just create a smaller table. This code assumes a fiarly recent version of MATLAB, but you can do more or less the same thing using earlier versions:

>> tt = timetable(rand(100,1),rand(100,1), ...
    'StartTime','1-Jan-2002','TimeStep',caldays(1), ...
    'VariableNames',["X" "Y"]);
>> ttJan2002 = tt(timerange('Jan-2002','months'),:)
ttJan2002 =
  31×2 timetable
       Time           X            Y    
    ___________    ________    _________
    01-Jan-2002     0.81472      0.16218
    02-Jan-2002     0.90579      0.79428
    03-Jan-2002     0.12699      0.31122
    04-Jan-2002     0.91338      0.52853
    05-Jan-2002     0.63236      0.16565
>> plot(ttJan2002.X,ttJan2002.Y);

I realize that sounds counter to what people have been saying, but for one plot, it's fine.

If you want to make thousands of such plots, then I would think you'd want to put that code into a loop, or use rowfun to make the plots. To use rowfun, you will probably want to add a couple of grouping variables to your timetable for monh and year number, using the month and year functions on your datetime.

Thomas Vescovini 2019-7-16