Create a MySQL-like ASCII table of data

asciify.R

asciify <- function(df, pad = 1, ...) {
    ## error checking
    stopifnot(is.data.frame(df))
    ## internal functions
    SepLine <- function(n, pad = 1) {
        tmp <- lapply(n, function(x, pad) paste(rep("-", x + (2* pad)),
                                                collapse = ""),
                      pad = pad)
        paste0("+", paste(tmp, collapse = "+"), "+")
    }
    Row <- function(x, n, pad = 1) {
        foo <- function(i, x, n) {
            fmt <- paste0("%", n[i], "s")
            sprintf(fmt, as.character(x[i]))
        }
        rowc <- sapply(seq_along(x), foo, x = x, n = n)
        paste0("|", paste(paste0(rep(" ", pad), rowc, rep(" ", pad)),
                          collapse = "|"),
               "|")
    }
    ## convert everything to characters
    df <- as.matrix(df)
    ## nchar in data
    mdf <- apply(df, 2, function(x) max(nchar(x)))
    ## nchar in names
    cnames <- nchar(colnames(df))
    ## max nchar of name+data per elements
    M <- pmax(mdf, cnames)
    ## write the header
    sep <- SepLine(M, pad = pad)
    writeLines(sep)
    writeLines(Row(colnames(df), M, pad = pad))
    writeLines(sep)
    ## write the rows
    for(i in seq_len(nrow(df))) {
        ## write a row
        writeLines(Row(df[i,], M, pad = pad))
        ## write separator
        writeLines(sep)
    }
    invisible(df)
}