Christine asked how to create efficient epicurves with an X axis grouping in time intervals.

I think the efficient way would be to change your date/time variables into hours since observation or a given day. Then cut the x-axis and work a bit on labelling.

That might sound easier than done (would take some time of experimentation). But for the development plan I think we should consider adding easier ways of doing that. E.g. to allow epicurve to scale the axis with different groupings, but also to find ways of managing time/date situations.

Some hints to the solution could be along these lines - A test could be: variables: dateonset : date of first symptom timeonset: hour at which the symptom came on that date (say the observations start on 1st of May this year) case: at least one positive symptom

* generate 50 test observations and an epicurve grouped by 3: Close generate 50 gen d dateonset=dmy(1,5,2008)+(recnumber mod 3) gen i timeonset = 24 mod recnumber gen i timevar = 24*(dateonset - dmy(1,5,2008)) + timeonset gen i case = recnumber mod 2

* epicurve by hour would then be epicurve timevar case

* recode hours to grouped hours by 3: define time3 ### recode timevar to time3 by 3 tab time3

* show epicurve: epicurve time3 case /xinc=3 /ti="Epicurve for ..... cases in 3 hour groups since start"

Notice that the time3 variable will have labels, but currently these are not added to the graph. But for just showing the graph the lines would work.

regards Jens Lauritsen EpiData Association