How do I get differences between groups over time from PROC MEANS with CLASS statement

[plf515]

Hello

I have a data set that has variables time (1 to 46); group (3 different groups) and alc (a numeric variable)

If I run

proc means data = ken.lsdalclong;
class time group;
var alc;
output out = ken.days mean = mean uclm = upper lclm = lower;
run;

then I get the mean, lcl and ucl of alc by time and group.  So far so good.

How can I get the differences between the means of the three groups by time?

That is, I want 46 values of (mean group 1 – mean group2) and 46 values of (mean group 1 – mean group3)?

Thanks

Peter

[Astounding · Accepted solution]

If you examine the output data set, you will see that you have the pieces that you need.  It is just a matter of extracting the right pieces and re-assembling them properly.  Here is a starting point:

proc transpose data=ken.days prefix=mean_group out=want;

id group;

var mean;

by time;

where _type_=3;

run;

Take a look first at KEN.DAYS to understand that the WHERE statement in PROC TRANSPOSE is selecting the proper observations.

Then take a look at the output data set WANT which will need a few more calculations, but has the data assembled in an easy-to-calculate form.