How to find average of few rows at a time

[pr1496]

Hi all, 

I am trying to set up a code that will automatically find the average of certain rows at a time. For example, in the data set below I want to find the average weight each month:

data have;
input id $ weight month;
cards;
1 108 1
1 112 1
1 114 2
1 118 2
2 100 1
2 108 1
2 110 2
2 102 2
2 100 2
;
run;

 So ideally, the new data table I want will look like this:

data want;
input id $ avg_weight month;
cards;
1 110 1
1 116 2
2 104 1
2 104 2
;
run;

Thanks for any/all help!

[sbxkoenk · Accepted solution]

proc means data=have nway noprint;
 CLASS id month;
 VAR   weight;
 output out=want mean= / autoname;
run;

Koen