Using for/while for a repeating task: average solar irradiation of every month

Hello everybody.

[MonthNum, MonthStr]=month(t), t is datetime

I tried to create MonthNum with the month function and comparing each element in the vector i, if its for example january. My Question is: can I use a loop for that task? I know that I can get two outputs from the month function, but it´s not workin for me. I thougt that I can use the MonthString for the name of the month.

Jan=mean(i(MonthNum==1),'omitnan');
Feb=mean(i(MonthNum==2),'omitnan');
Mar=mean(i(MonthNum==3),'omitnan');
Apr=mean(i(MonthNum==4),'omitnan');
Mai=mean(i(MonthNum==5),'omitnan');
Jun=mean(i(MonthNum==6),'omitnan');
Jul=mean(i(MonthNum==7),'omitnan');
Aug=mean(i(MonthNum==8),'omitnan');
Sep=mean(i(MonthNum==9),'omitnan');
Okt=mean(i(MonthNum==10),'omitnan');
Nov=mean(i(MonthNum==11),'omitnan');
Dez=mean(i(MonthNum==12),'omitnan');
Year=[iJan;iFeb;iMar;iApr;iMai;iJun;iJul;iAug;iSep;iOkt;iNov;iDez];

%maybe like that:
for k=1:12
    MonthString(k)=mean(i(MonthNum==k),'omitnan');
end

I never came to the part with the for loop because the month function creates an error: too many output arguments.

Thanks for helping