[R] Automating plot labelling in custom function in lapply( ) ?

[Liaw, Andy]

> From: Marc Schwartz
> 
> On Fri, 2005-04-29 at 13:00 +0100, Gavin Simpson wrote:
> > Dear List,
> > 
> > Consider the following example:
> > 
> > dat <- data.frame(var1 = rnorm(100), var2 = rnorm(100),
> >                    var3 = rnorm(100), var4 = rnorm(100))
> > oldpar <- par(mfrow = c(2,2), no.readonly = TRUE)
> > invisible(lapply(dat,
> >                   function(x) {
> >                     plot(density(x),
> >                          main = deparse(substitute(x))) }
> >                   )
> >            )
> > par(oldpar)
> > 
> > I want to the main title in each of the density plots to be 
> var1, var2, 
> > etc. The above code produces x[[1]], x[[2]] etc.
> > 
> > What do I need to modify to be able to use the name of x as 
> the plot 
> > label within in the above situation?
> > 
> > Thanks in advance,
> > 
> > Gav
> 
> Gavin,
> 
> To paraphrase John Fox from a recent thread, "this is one of 
> those times
> where trying to avoid using a for() loop is counterproductive":
> 
> oldpar <- par(mfrow = c(2,2), no.readonly = TRUE)
> 
> for (i in 1:4)
> {
>   plot(density(dat[, i]), main = colnames(dat)[i])
> }
> 
> par(oldpar)
> 
> 
> HTH,
> 
> Marc Schwartz

For things like these I'd suggest using lattice; e.g.,

densityPlot <- function(dat, xlab=deparse(substitute(dat)), ...) {
    stopifnot(require(lattice))
    vars <- rep(colnames(dat), each=nrow(dat))
    densityplot(~ c(as.matrix(dat)) | vars, xlab=xlab, ...)
}

densityPlot(dat, layout=c(2, 2))

Cheers,
Andy

 
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