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#!/usr/bin/awk
### mean_avg.awk
# average columns of numerical data
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] = $n
}
}
# Welford's 'online' algorithm for variance
NF != 0 {
if (NF > max_nf)
max_nf = NF
for (n=1; n <= NF; n++) {
if ($n ~ number) {
count[n] += 1
delta0[n] = $n - mean[n]
mean[n] = mean[n] + delta0[n]/count[n]
delta1[n] = $n - mean[n]
M2[n] = M2[n] + delta0[n]*delta1[n]
if (count[n] > 1)
var[n] = M2[n]/(count[n] - 1)
else
var[n] = "0"
}
}
}
END {
printf("\n")
printf("%s, \t%s, %s, %s, %s\n", "col", "mean", "std_dev", "std_err", "count")
for (n=1; n<=max_nf; n++) {
if (header[n])
printf("%s, \t", header[n])
else
printf("col_%g, \t", n)
if (count[n]) {
printf("%g, ±%g, ±%g, %g\n",
mean[n], sqrt(var[n]), 1.96*sqrt(var[n]/count[n]), count[n])
}
else
printf(",,,,\n")
}
}
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