[R] Boxplot- input the median point and the median value

[Jim Lemon]

On 01/02/2010 12:53 PM, elaine kuo wrote:
>   Dear,
>
> I am a newbie to R.
>
> Now I am learning to draw boxplot using graphics().
>
> I want to highlight the median position
>
> with a round point and the value left (or on the top of)to the point.
>
>
>    
Hi Elaine,

For your boxplot questions, I'll use the first example from the boxplot 
help page:

boxplot(count ~ spray, data = InsectSprays,
  col = "lightgray",yaxt="n")
axis(2,c(2,8,14,20),c(2,8,14,20))

For the "dotted to solid" question:

boxplot_info<-boxplot(count ~ spray,
  data = InsectSprays,col = "lightgray")
segments(rep(1:6,each=2),boxplot_info$stats[c(1,4),],
  rep(1:6,each=2),boxplot_info$stats[c(2,5),])

And finally, for the median value question:

boxplot_info<-boxplot(count ~ spray, data = InsectSprays,
  col = "lightgray")
points(1:6,boxplot_info$stats[3,])
text(1:6,boxplot_info$stats[3,]+1,boxplot_info$stats[3,])

A bit messy, but you get the idea.

Jim