Monthly data to seasonal using sum (how to use splitapply)

Hi, I wish you are safe and healthy!

I have a 1 x 3 cell with three 360 x 3 table. Each table has a column date with 30 years of monthly data (30 x 12 = 360). I want to have data for seasonal scale, winter, spring, summer and autumn correspond to December–February, March-May, June–August, and September–November, respectively using sum. I would like to create each season in a separate column with the corresponding name of the season and located after all existing columns in the tables.

Thank you so much

Answer 1

[Peng Li]

Try below

tbl = CELL{1};

tbl.month = month(tbl.dates);
tbl.season = floor(tbl.month ./ 3);
tbl.season(tbl.season == 4) = 0;
tbl.season = categorical(tbl.season, [0 1 2 3], ["Spr", "Sum", "Aut", "Win"]);

You can use findgroups to group them based on seasons and use varfun or splitapply to calculate sum.

[BN]

Thank you dear Peng Li,

I try this and then read findgroups documantation and using this line in order to get sum of spring seasons:

season = findgroups(tbl.season);
splitapply(@sum,season,tbl)

But it doesnt work and gave me this error:

Error using splitapply (line 61)
Group numbers must be a vector of positive integers, and cannot be a
sparse vector. 

If you please could you show me an example for one season?

Thank you.

[Peng Li]

The second parameter of splitapply should be the table and group parameter should be on the third place if I remember correctly.

[Peng Li]

will have an example later. Using cellphone now.

[Peng Li]

>> [grp, meanTbl] = findgroups(tbl(:, 'season'));
>> meanTbl.rrr24 = splitapply(@mean, tbl.rrr24, grp);
>> meanTbl

meanTbl =

  4×2 table

    season    rrr24 
    ______    ______

     Spr      14.038
     Sum      35.004
     Aut      10.949
     Win      16.958

[BN]

Thank you