#!/usr/bin/awk -f

### diff.awk
# numerical diff along columns

BEGIN {
    sign = "[+-]?"
    decimal = "[0-9]+[.]?[0-9]*"
    fraction = "[.][0-9]*"
    exponent = "([Ee]" sign "[0-9]+)?"
    number = "^" sign "(" decimal "|" fraction ")" exponent "$"
}

NR == 1 {
    header_nf = NF
    for (n=1; n<=NF; n++) {
        if ($n !~ number)
            header[n] = "d" $n
        else
            header[n] = "col_" n
        printf("%s,", header[n])
    }
}

NF != 0 {
    if (NF > max_nf)
        max_nf = NF

    ### iterate over columns
    for (y=1; y<=max_nf; y++) {
        if ($y ~ number) {

            data[y] = $y
            diff[y] = data[y] - data_prev[y]
            printf("%g,", diff[y])
            data_prev[y] = data[y]

        }
    }
    printf("\n")
}