[R] legend in R plot

[Jim Lemon]

On 07/22/2010 02:06 PM, li li wrote:
> Hi all,
>    I am have some difficulty with the legend function.
>    I need to add a legend to describe the different line types in a plot. The
> legend box is small.
> It did not include sufficient length of each line type to help distinguish
> the differnt line types.
>    Is there a way to fix this.

Hi Hannah,
I thought that there was some argument to specify the horizontal 
proportion of the legend box devoted to text, but I can't find it. 
Perhaps you could roll your own legend using the rect, text and line 
functions.

wide.legend<-function(x,y=NA,legend,lty=1,lwd=1,bg=par("bg"),
  border=par("fg"),col=par("fg"),cex=1,
  xjust=0,yjust=1,text.prop=0.5,...) {

  if(is.na(y) && is.list(x)) {
   y<-unlist(x[[2]])
   x<-unlist(x[[1]])
  }
  boxwidth<-(max(strwidth(legend))+strwidth("o"))/text.prop
  boxheight<-strheight(paste(legend,collapse="\n"))+strheight("o")
  boxleft<-x-boxwidth*xjust
  boxbottom<-y-boxheight*yjust
  rect(boxleft,boxbottom,boxleft+boxwidth,
   boxbottom+boxheight,col=bg,border=border)
  text(boxleft+boxwidth*(1-text.prop),
   boxbottom+1:length(legend)*strheight("O"),
   legend,cex=cex,adj=c(0,0.5),...)
  hgap<-strwidth("o")
  segments(boxleft+hgap,
   boxbottom+1:length(legend)*strheight("O"),
   boxleft+boxwidth*(1-text.prop)-hgap,
   boxbottom+1:length(legend)*strheight("O"),
   lty=lty,lwd=lwd,col=col)
}

Pretty rough, but it's a start

Jim