The R Project SVN R

curve <- function(expr, from, to, n=101, add=FALSE, type="l",
          ylab = NULL, log=NULL, ...)
{
    sexpr <- substitute(expr)
    if(is.name(sexpr)) {
    fcall <- paste(sexpr, "(x)")
    expr <- parse(text=fcall)
    if(is.null(ylab)) ylab <- fcall
    } else {
    if(!(is.call(sexpr) && match("x", all.vars(sexpr), nomatch=0)))
        stop("'expr' must be a function or an expression containing 'x'")
    expr <- sexpr
    if(is.null(ylab)) ylab <- deparse(sexpr)
    }
    lims <- delay(par("usr"))
    if(missing(from)) from <- lims[1]
    if(missing(to)) to <- lims[2]
    lg <- if(length(log)) log else ""
    x <-
    if(lg != "" && "x" %in% strsplit(lg, NULL)[[1]]) {
        ## unneeded now: rm(list="log",envir=sys.frame(1))# else: warning
        if(any(c(from,to)<=0))
        stop("`from' & `to' must be > 0  with  log=\"x\"")
        exp(seq(log(from), log(to), length=n))
    } else seq(from,to,length=n)
    y <- eval(expr, envir=list(x = x), enclos=sys.frame(sys.parent(1)))
    if(add)
    lines(x, y, type=type, ...)
    else
    plot(x, y, type=type, ylab = ylab, log=lg, ...)
}