The R Project SVN R-packages

## This is a modification of text.tree.
## Fancy option has been added in (to mimic post.tree)
##

text.rpart <-
    function(x, splits = TRUE, label, FUN = text, all = FALSE,
             pretty = NULL, digits = getOption("digits") - 3L,
             use.n = FALSE, fancy = FALSE, fwidth = 0.8, fheight = 0.8,
             bg = par("bg"), minlength = 1L, ...)
{
    if (!inherits(x, "rpart")) stop("Not a legitimate \"rpart\" object")
    if (nrow(x$frame) <= 1L) stop("fit is not a tree, just a root")

    frame <- x$frame
    if (!missing(label)) warning("argument 'label' is no longer used")
    col <- names(frame)
    ylevels <- attr(x, "ylevels")
    if (!is.null(ylevels <- attr(x, "ylevels"))) col <- c(col, ylevels)
    cxy <- par("cxy")                   # character width and height
    if (!is.null(srt <- list(...)$srt) && srt == 90) cxy <- rev(cxy)
    xy <- rpartco(x)

    node <- as.numeric(row.names(frame))
    is.left <- (node %% 2L == 0L)            # left hand sons
    node.left <- node[is.left]
    parent <- match(node.left/2L, node)

    ## Put left splits at the parent node
    if (splits) {
        left.child <- match(2L * node, node)
        right.child <- match(node * 2L + 1L, node)
        rows <- if (!missing(pretty) && missing(minlength))
            labels(x, pretty = pretty) else labels(x, minlength = minlength)
        if (fancy) {
            ## put split labels on branches instead of nodes
            xytmp <- rpart.branch(x = xy$x, y = xy$y, node = node)
            leftptx <- (xytmp$x[2L, ] + xytmp$x[1L, ])/2
            leftpty <- (xytmp$y[2L, ] + xytmp$y[1L, ])/2
            rightptx <- (xytmp$x[3L, ] + xytmp$x[4L, ])/2
            rightpty <- (xytmp$y[3L, ] + xytmp$y[4L, ])/2

            FUN(leftptx, leftpty + 0.52 * cxy[2L],
                rows[left.child[!is.na(left.child)]], ...)
            FUN(rightptx, rightpty - 0.52 * cxy[2L],
                rows[right.child[!is.na(right.child)]], ...)
        } else
            FUN(xy$x, xy$y + 0.5 * cxy[2L], rows[left.child], ...)
    }

    leaves <- if (all) rep(TRUE, nrow(frame)) else frame$var == "<leaf>"

    stat <-
        x$functions$text(yval = if (is.null(frame$yval2)) frame$yval[leaves]
                                else frame$yval2[leaves, ],
                         dev = frame$dev[leaves], wt = frame$wt[leaves],
                         ylevel = ylevels, digits = digits,
                         n = frame$n[leaves], use.n = use.n)

    if (fancy) {
        if (col2rgb(bg, alpha = TRUE)[4L, 1L] < 255) bg <- "white"
        oval <- function(middlex, middley, a, b)
        {
            theta <- seq(0, 2 * pi, pi/30)
            newx <- middlex + a * cos(theta)
            newy <- middley + b * sin(theta)
            polygon(newx, newy, border = TRUE, col = bg)
        }

        ## FIXME: use rect()
        rectangle <- function(middlex, middley, a, b)
        {
            newx <- middlex + c(a, a, -a, -a)
            newy <- middley + c(b, -b, -b, b)
            polygon(newx, newy, border = TRUE, col = bg)
        }

        ## find maximum length of stat
        maxlen <- max(string.bounding.box(stat)$columns) + 1L
        maxht <- max(string.bounding.box(stat)$rows) + 1L

        a.length <- if (fwidth < 1)  fwidth * cxy[1L] * maxlen else fwidth * cxy[1L]

        b.length <- if (fheight < 1) fheight * cxy[2L] * maxht else fheight * cxy[2L]

        ## create ovals and rectangles here
        ## sqrt(2) creates the smallest oval that fits around the
        ## best fitting rectangle
        for (i in parent)
            oval(xy$x[i], xy$y[i], sqrt(2) * a.length/2, sqrt(2) * b.length/2)
        child <- match(node[frame$var == "<leaf>"], node)
        for (i in child)
            rectangle(xy$x[i], xy$y[i], a.length/2, b.length/2)
    }

    ##if FUN=text then adj=1 puts the split label to the left of the
    ##    split rather than centered
    ##Allow labels at all or just leaf nodes

    ## stick values on nodes
    if (fancy) FUN(xy$x[leaves], xy$y[leaves] + 0.5 * cxy[2L], stat, ...)
    else FUN(xy$x[leaves], xy$y[leaves] - 0.5 * cxy[2L], stat, adj = 0.5, ...)

    invisible()
}