[R] plot.function with xlim, bug?

[Prasenjit Kapat]

Consider the following lines of code:

     plot(function(x) sin(cos(x)*exp(-x/2)), from=-8,to=7,xlim=c(-5,5))
Uses integral points (integers from -5 to 5) to draw the plot, instead
of the usual default of n= 101 "equally spaced points" (from
?plot.function).

    plot(function(x) sin(cos(x)*exp(-x/2)), from=-8,to=7,n=101,xlim=c(-5,5))
Gives the following error:
Error in add && par("xlog") : invalid 'x' type in 'x && y'

Any explanations? The following modification, in the plot.R by NOT
passing 'y' to plot.function, seems to fix both of the above problems
! I am sure to be missing something!

"plot2" <- function (x, y, ...)
{
    if (is.null(attr(x, "class")) && is.function(x)) {
        nms <- names(list(...))
        ## need to pass 'y' to plot.function() when positionally matched "????"
        if(missing(y)) # set to defaults {could use formals(plot.default)}:
            y <- { if (!"from" %in% nms) 0 else
                   if (!"to"   %in% nms) 1 else
                   if (!"xlim" %in% nms) NULL }
        if ("ylab" %in% nms)
            plot.function(x, ...)
        else
            plot.function(x, ylab=paste(deparse(substitute(x)),"(x)"), ...)
    }
    else UseMethod("plot")
}
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version.string R version 2.4.1 (2006-12-18)
platform   i486-pc-gnu-linux