Highlights cells, such as the maxima in each column or row, of an 'xtable' in R

xtable_printbold.R

## 2010-06-25
## (c) Felix Andrews <felix@nfrac.org>
## GPL-2

## If 'which' is given it should be a logical matrix specifying bold cells.
## Otherwise: in each column or row with numeric data, the maximum or minimum 
## value is set bold; 'max' can have entries for each column/row, NA means skip.

## Examples:
## library(xtable)
## x <- tail(iris)
## printbold(xtable(x)) #each = "column"
## printbold(xtable(x), each = "column", max = c(F,NA,NA,T,NA))
## printbold(xtable(x), each = "row", max = FALSE)
## printbold(xtable(x), x >= 6.5, type = "html")

printbold <-
    function(x, which = NULL, each = c("column", "row"), max = TRUE,
             NA.string = "", type = c("latex", "html"),
             sanitize.text.function = force,
             sanitize.rownames.function = NULL,
             sanitize.colnames.function = NULL, ...)
{
    stopifnot(inherits(x, "xtable"))
    each <- match.arg(each)
    type <- match.arg(type)
    digits <- rep(digits(x), length = ncol(x)+1)
    if (!is.null(which)) {
        stopifnot(nrow(which) == nrow(x))
        stopifnot(ncol(which) == ncol(x))
        boldmatrix <- which
    } else {
        boldmatrix <- matrix(FALSE, ncol = ncol(x), nrow = nrow(x))
        ## round values before calculating max/min to avoid trivial diffs
        for (i in 1:ncol(x)) {
            if (!is.numeric(x[,i])) next
            x[,i] <- round(x[,i], digits = digits[i+1])
        }
        if (each == "column") {
            max <- rep(max, length = ncol(x))
            for (i in 1:ncol(x)) {
                xi <- x[,i]
                if (!is.numeric(xi)) next
                if (is.na(max[i])) next
                imax <- max(xi, na.rm = TRUE)
                if (!max[i])
                    imax <- min(xi, na.rm = TRUE)
                boldmatrix[xi == imax, i] <- TRUE
            }
        } else if (each == "row") {
            max <- rep(max, length = nrow(x))
            for (i in 1:nrow(x)) {
                xi <- x[i,]
                ok <- sapply(xi, is.numeric)
                if (!any(ok)) next
                if (is.na(max[i])) next
                imax <- max(unlist(xi[ok]), na.rm = TRUE)
                if (!max[i])
                    imax <- min(unlist(xi[ok]), na.rm = TRUE)
                whichmax <- sapply(xi, identical, imax)
                boldmatrix[i, whichmax] <- TRUE
            }
        }
    }
    ## need to convert to character
    ## only support per-column formats, not cell formats
    display <- rep(display(x), length = ncol(x)+1)
    for (i in 1:ncol(x)) {
        if (!is.numeric(x[,i])) next
        ina <- is.na(x[,i])
        x[,i] <- formatC(x[,i], digits = digits[i+1],
                         format = display[i+1])
        x[ina, i] <- NA.string
        display(x)[i+1] <- "s"
        ## embolden
        yes <- boldmatrix[,i]
        if (type == "latex") {
            x[yes,i] <- paste("\\textbf{", x[yes,i], "}", sep = "")
        } else {
            x[yes,i] <- paste("<strong>", x[yes,i], "</strong>", sep = "")
        }
    }
    print(x, ..., type = type, NA.string = NA.string,
          sanitize.text.function = sanitize.text.function,
          sanitize.rownames.function = sanitize.rownames.function,
          sanitize.colnames.function = sanitize.colnames.function)
}