[R] Help with evaluation of expressions

[Dieter Menne]

Michael Conklin <michael.conklin <at> markettools.com> writes:

> 
> I have searched through the help files and I have been unsuccessful in
> solving this problem.
> 
> I am trying to create a small wrapper function that will go around a
> call to a plot function and create a windows metafile in the directory
> and also write the name of the file to a text file. The purpose is to
> efficiently bring a large number of plots into powerpoint.  I am using
> platform      

Try this variant. Note that I am using emf instead of wmf, it's a bit more
stable. And I had to prepare an undecorated filename since savePlot has special
ideas about appending appendixes. 

Please, if you post, provide a full working demo example next time, not only the
function. There are only few genius who can see the right way without firing up
the gui.

Dieter
------

plotSlide<-function(pltexpr){
  expr<-as.expression(pltexpr)
  numslide<-length(dir(pattern="emf"))+1
  fname0<-paste("SG",numslide,sep="")
  fname<-paste(fname0,".emf",sep="")
  dirlist<-dir(pattern="SlideList.txt")
  if (length(dirlist)==1){
    fs<-file("SlideList.txt",open="at")
    write(paste(fname,"Graph",sep=","),file=fs)
    close(fs)} else {
    write(paste(fname,"Graph",sep=","),file="SlideList.txt")
    }
  p=eval(pltexpr)
  if (is.null(p)) {
    savePlot(fname0,type="emf")
  } else {
    trellis.device(device = win.metafile, theme = "col.whitebg", new =
TRUE, retain = FALSE, file=fname,width=6,height=4)
    print(p)
  }
  dev.off()
  fname
}

plotSlide(
  plot(rnorm(100))
)

library(lattice)
plotSlide(
  xyplot(Sepal.Length  ~ Petal.Length, data = iris)
)