/*Example 1*/ use drug, clear datacheck drug=="aspirin" if arm==1, varshow(id drug arm) message(Wrong drug) /*Example 2*/ use visits, clear datacheck date>date[_n-1] if _n>1, varshow(visit date) message(Dates do not follow) prev /*Example 3*/ use scores, clear sort id time datacheck time==0 if _n==1, by(id) varshow(id time) message(Patient's first record is not at time 0)