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#!/usr/bin/awk -f

### cov.awk
# online covariance algorithm


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


# column headers
NR == 1 {
    for (n=1; n<=NF; n++)
        ($n ~ number) ? header[n] = "col" n : header[n] = $n
}


NF > 0 {
    (NF > nf_max) ? nf_max = NF : nf_max = nf_max

    # columns
    for (y=1; y<=nf_max; y++) {
        # rows
        for (x=1; x<=nf_max; x++) {
            if ($x !~ number || $x == header[x])
                continue
            count[x,y]++
            dx[x,y] = $x - meanx[x,y]
            dy[x,y] = $y - meany[x,y]
            meanx[x,y] += dx[x,y]/count[x,y]
            meany[x,y] += dy[x,y]/count[x,y]
            C[x,y] += dx[x,y]*dy[x,y]
            (count[x,y] > 1) ? cov_samp[x,y] = C[x,y]/(count[x,y] - 1) : cov_samp[x,y] = ""
        }
    }
}


END {
    # column headers
    printf("cov")
    for (y=1; y<=nf_max; y++) {
        printf(OFS header[y])
    }
    printf(ORS)

    # columns
    for (y=1; y<=nf_max; y++) {
        printf(header[y] OFS)
        # rows
        for (x=1; x<=nf_max; x++) {
            printf(OFMT, cov_samp[x,y])
            if (x < nf_max)
                printf(OFS)
        }
        printf(ORS)
    }
}