#!/usr/bin/awk -f

### diff.awk
# numerical diff along columns

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

NR == 1 {
    ### orig columns
    for (n=1; n<=NF; n++) {
        ($n !~ number) ? header[n] = $n : header[n] = "col" n
        printf(header[n])
        ($n !~ number) ? dheader[n] = "d" $n : dheader[n] = "dcol" n
        if (n <= NF)
            printf(OFS)
    }

    ### diff columns
    for (n=1; n<=NF; n++) {
        printf(dheader[n])
        if (n < NF)
            printf(OFS)
    }
}

NF {
    if (NF > nf_max)
        nf_max = NF

    ### orig columns
    for (y=1; y<=nf_max; y++) {
        if ($y == header[y] || $y == dheader[y])
            continue
        if ($y ~ number)
            printf($y)
        else
            printf("")
        printf(OFS)
    }

    ### diff columns
    for (y=1; y<=nf_max; y++) {
        if ($y ~ number) {
            data[y] = $y
            (data_prev[y] ~ number) ? diff[y] = data[y] - data_prev[y] : diff[y] = ""
            data_prev[y] = data[y]
            printf(diff[y])
            if (y < nf_max)
                printf(OFS)
        }
        diff[y] = ""
    }
    printf("\n")
}