I've succeeded doing a subset within the panel function of xyplot - if I'm subsetting based on either the value of 'x' or 'y' (e.g. below).  However, I wish to subset based on the value of another variable and colour that one plotted point.  It's not working.  Either it doesn't plot the coloured data point, or if I sort the data differently it colours one datapoint, but the wrong one.   I assume this means it's not getting the right subscripts?    Finally I can sort of see the light as if I remove the conditioning variable (week) and subset before the xyplot (e.g. week==1) to get just one panel, it plots the correct data including the correct single red point.
Where am I erring?
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print(xyplot(yval~xval|week,data=mydata,
 panel=function(x,y,subscripts){
	#panel.xyplot(x,y,type='p',col=1,cex=.5)
	panel.xyplot(x[y<=40],y[y<=40],type='p',col=2,cex=.5)  #  <-----this works
	panel.xyplot(x[mydata$yr==2005],y[mydata$yr==2005],type='p',pch=16,col=2,cex=.5)  #  <-----sometimes this won't work or it colours wrong datapoint
}))
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Thanks very much!
Michael Folkes
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Michael Folkes
Salmon Stock Assessment
Canadian Dept. of Fisheries & Oceans     
Pacific Biological Station
3190 Hammond Bay Rd.
Nanaimo, B.C., Canada
V9T-6N7
Ph (250) 756-7264 Fax (250) 756-7053  folkesm@pac.dfo-mpo.gc.ca


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