How do I create a for loop to group data?

Hello everyone

I have set a set of annual data which I would like to group into seasons. I can do this through concatenation of the individual months as below:

jan= SUNdat(1==month(SUNdat.Date),:);
feb= SUNdat(2==month(SUNdat.Date),:);
mar= SUNdat(3==month(SUNdat.Date),:);
dec= SUNdat(12==month(SUNdat.Date),:);
Summer=[jan;feb;mar;dec];

This is a longer way. So instead I a trying to implement a for loop as below but it is not working

n=1:3;
 for n=3
    summer=SUNdata(n==month(SUNdat.Date),:);
    n=n+1;
 end
    

This returns an error. How else can I implement this to be able to group my data as explained

[madhan ravi]

could you provide a sample data?

[Sheng Chen]

Could you please also provide the error message?