ref: be8119e06b08bc31f654ffe71628507bb09c4b4a
dir: /awk/descstat.awk/
#!/bin/awk -f # assumption: no missing values/indices in input data function swap(X, a, b, t) { t = X[a] X[a] = X[b] X[b] = t } # from numerical recipes 3rd ed; rearranges X function select(X, k, i, j, n, m, l, ir) { l = 1 ir = length(X) for(;;){ if(ir <= l+1){ if(ir == l+1 && X[ir] < X[l]) swap(X, l, ir) return int(X[k]) }else{ m = (l + ir) / 2 swap(X, m, l+1) if(X[l] > X[ir]) swap(X, l, ir) if(X[l+1] > X[ir]) swap(X, l+1, ir) if(X[l] > X[l+1]) swap(X, l, l+1) i = l + 1 j = ir m = X[l+1] for(;;){ do i++; while(X[i] < m) do j--; while(X[j] > m) if(j < i) break swap(X, i, j) } X[l+1] = X[j] X[j] = m if(j >= k) ir = j - 1 if(j <= k) l = i } } } function max(X, n) { n = "-inf" for(i in X) if(X[i] > n) n = X[i] return n } function min(X, n) { n = "inf" for(i in X) if(X[i] < n) n = X[i] return n } function sum(X, i, n) { for(i in X) n += X[i] return n } function mean(X) { return sum(X) / length(X) } function var(X, i, n, m) { m = mean(X) for(i in X) n += (X[i] - m) ^ 2 return n / (length(X) - 1) } function sd(X) { return sqrt(var(X)) } # FIXME: this is wrong and produces wrong results in subsequent stuff # select is busted # rearranges X function median(X, n) { n = select(X, int(length(X) / 2 + 1)) if(length(X) % 2 != 0) return n else return (select(X, int(length(X) / 2)) + n) / 2 } function freq(X) { delete ans for(i in X) ans[X[i]]++ }