I am doing group wise plots by using the following commands; it shows
errors that I do not know how to fix it. Please help.
 
 
 
xyplot(within.2.special.care ~ agecat| mco.cms.ind, neuro, panel =
function(x,y){
+ panel.grid()
+ panel.xyplot(x,y)
+ panel.loess(x,y, span =1)})
 
Error: couldn't find function "xyplot"

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