I am using the command
qplot(factor(ww), WeeklyYield, geom = "bar", fill = I("grey50"))+facet_wrap(~model+name)
to create a bar chart for every combination of model
and name
. However I get the following error message:
Error in layout_base(data, vars, drop = drop) : At least one layer must contain all variables used for facetting
I cannot uncode this message.