Question

I m plotting a group of curves, using facet in ggplot2. I d like to have a smoother applied to plots where there are enough points to smooth, but not on plots with very few points. In particular I d like to stop the plot failing when one of the panels only has 1 or 2 points.

Example:

a <- data.frame( x=1:100, y=sin(seq(0.1,10,0.1) )) 
b <- data.frame( x=1:5, y=sin(seq(0.1,0.2,0.1) )) 
l <- melt(list(a=a,b=b),id.vars="x") 
qplot( x, value, data=l ) + geom_smooth() + facet_wrap( ~ L1 )

Answer 1

Try this

library(ggplot2)
a <- data.frame( x=1:100, y=sin(seq(0.1,10,0.1) )) 
b <- data.frame( x=1:2, y=sin(seq(0.1,0.2, length = 2) )) 
l <- melt(list(a=a,b=b),id.vars="x") 

more_than <- function(n) {
  function(df)  {
    if (nrow(df) > n) {
      df
    }
  }
}

lbig <- ddply(l, "L1", more_than(5))

qplot( x, value, data=l ) + geom_smooth() + facet_wrap( ~ L1 )
qplot( x, value, data=l ) + geom_smooth(data = lbig) + facet_wrap( ~ L1 )

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