I constructed a mmrm model as below: proc mixed data = have; class id treatment week strata; model chg = base treatment week treatment*week treatment*strata/ ddfm = KR; repeated week/ subject = id type = UN; lsmeans treatment*week/ cl alpha = 0.05 diff ods output Tests3=tests3 lsmeans=lsmeans diffs=diffs; run; (1) id: represents the patient id; (2) treatment: contains 2 group, "drug" and "placebo"; (3) chg: change from baseline of hba1c; (4) base: the value of hba1c at baseline; (5) week: contains 3 levels: "week8", "week16" and "week24" (6 )strata: stratification based on the median of baseline hba1c, ie       group1=patients of those who have baseline hba1c <= median of baseline hba1c;       group2=patients of those who have baseline hba1c > median of baseline hba1c.   In general, I'd like to know how to the test the interaction between strata and treatment groups. I am not sure if I constructed the model in a right way because I looked at the results (as below), the values of Diffs in LS means were pretty close between strata, but p for interaction was significant. (The Diffs in LS means were got from the output file diffs, and the p for interaction were got from the output file test3.) I also checked the Diffs in LS means of week8 and week16, the diffs in LS means were all pretty close between 2 strata, but the p for interaction were all significant (p-value < 0.0001). So I am not sure if I interpret the result in the right way. What data should look quite different if the p for interaction is statistically significant? Thanks. ... View more

I performed a mmrm model as below:   proc mixed data = have; class id treatment week strata; model chg = baseline treatment week treatment*week treatment*strata/ ddfm = KR; repeated week/ subject = id type = UN; lsmeans treatment*week/ cl alpha = 0.05 diff ods output Tests3=tests3 lsmeans=lsmeans diffs=diffs; run; In the model:   (1) id: represents the patient id, ie 101,102,103.... (2) chg: represents the change from baseline of hba1c (3) baseline: the value of hba1c at baseline (4) treatment: contains 2 categories: "drug" and "placebo" (5) week: contrains 3 levels: week8, week16, week24 (6) strata: represents the stratification by the median of hba1c at baseline, ie:        group1=patient of those who have hba1c at baseline <= median of hba1c at baseline;        group2=patient of those who have hba1c at baseline > median of hba1c at baseline.   In general, I'd like to test the interaction between strata and treatment, but I am not sure if I performed the test in the right way. Because I checked the results (as below), the column of "Diffs in LS means" were pretty close between strata, however the interaction p-value is statistically significant. (The values of Diffs in LS means were got from the output file diffs, and the p for interaction were got from the output file test3.) I also checked the Diffs in LS means not only at week24, but also week 8 and week16, they all looked pretty close between strata. So did I interpret the data in a wrong way? Or did I perform the model in a wrong way? What data should look different if the p for interaction is significant? Thanks! ... View more

I saw a loop code the other day. And it generate files of output_&i (i.e. output_1, output_2,..., output_n). At the end, it row bind all the files as: data all_results; set output_:; run; It seems that we could list files output_1, output_2, ... , output_n in a simple way by using ":" as output_:, so I tried to row bind my files that all end up with "_output" (i.e. 1_output, 2_output, 3_output) in a similar way:   data all_results; set :_output; run; But it failed. I'd like to know how to write the code in the right way. Thanks! ... View more

I have a column called startdate with time values, like: 30JUN1948:00:00:00.000 07JAN1967:00:00:00.000 01FEB1953:00:00:00.000 ... When I tried to pass the time value to a new variable called start,  like this: data want; set data have; start = startdate; run; The new column start looked like this: -363052800 221443200 -218160000 ...   I'd like to know how to pass the date time value to the new column with its original format? Thanks.       ... View more