p.s., The logic behind the method is described at: http://www.sascommunity.org/wiki/Look-Ahead_and_Look-Back

Art ---------- On Wed, 7 Jul 2010 13:41:08 -0700, Arthur Tabachneck <art297@NETSCAPE.NET> wrote:

>Al, > >I think that the look ahead look back code proposed by Howard Schreier >a few years ago will do exactly what you want. E.g., > >data have; > format dt date9.; > informat dt date9.; > input pat vis dt date9.; > cards; >1 1 11FEB2010 >1 2 13FEB2010 >1 3 14FEB2010 >2 1 11MAR2010 >2 2 06MAR2010 >2 3 20MAR2010 >3 1 05MAY2010 >3 2 08MAY2010 >3 3 12MAY2010 >3 4 10MAY2010 >; > >data want (drop=next: prev:); > set have; > by pat; > call missing(flag); > set have ( firstobs = 2 keep = dt > rename = (dt = next_dt) ) > have ( obs = 1 drop = _all_ ); > format prev_dt next_dt date9.; > prev_dt=lag(dt); > if last.pat then next_dt=.; > if (not(missing(next_dt)) and dt gt next_dt) or > dt lt prev_dt > then flag=1; >run; > >HTH, >Art >------------ >On Jul 7, 2:38 pm, Al <ali6...@gmail.com> wrote: >> Dear all: >> >> This is the dataset i have .. >> >> pat vis dt >> 1 1 11FEB2010 >> 1 2 13FEB2010 >> 1 3 14FEB2010 >> 2 1 11MAR2010 >> 2 2 06MAR2010 >> 2 3 20MAR2010 >> 3 1 05MAY2010 >> 3 2 08MAY2010 >> 3 3 12MAY2010 >> 3 4 10MAY2010 >> >> I am trying to get to this dataset with a flag variable >> to see if any of the dt values are placed out of the order per pat >> >> pat vis dt flag >> 1 1 11FEB2010 >> 1 2 13FEB2010 >> 1 3 14FEB2010 >> 2 1 11MAR2010 1 >> 2 2 06MAR2010 1 >> 2 3 20MAR2010 >> 3 1 05MAY2010 >> 3 2 08MAY2010 >> 3 3 12MAY2010 1 >> 3 4 10MAY2010 1 >> >> Any suggestions >> >> Thanks in advance >> Al