a function to generate Pandoc compatible markdown tables from R

markdownTable.R

#' A function to generate markdown tables for R data
#'
#' This function willl generate pandoc compatible markdown for tables from R data
#' @param df a \code{data.frame}
#' @param  headings = NULL headings to use if one desires something other than default \code{data.frame} column names
#' @export
#' @examples \dontrun{
#' markdownTable(mtcars)
#'}
markdownTable <- function(df, headings = NULL) {
	if(!is(df, "data.frame"))
		stop("markdownTable currently only supports data.frame", call.=F)

if(!is.null(headings) && length(headings)!=ncol(df))
	stop("Headings don't match dimentions of data.frame")
 
 # First create column width to the max nchar of each col
 max_lengths <- rbind(apply(df, 2, nchar),sapply(names(df), length))
 colwidths <- apply(max_lengths, 2, function(x) max(x))
 topline <- str_pad("-", (sum(colwidths) + 7), pad="-")
 # this line above doesn't work
 headings <- str_pad(paste0("*", names(df), "*"), round(max(colwidths)/2), "both")
 

 cat(topline)
 # cat the data
 cat(headings)
 cat(topline)
 # More issues remain. I need to pad each row element to the max width of that row.
 # Then I need to cat the whole thing to screen all at once.
}