ref: 2850b592998277aef88f3e6769063b741d850d58
parent: d13e97eec68079ee7efabb2714427276dcd9ea6f
author: qwx <qwx@sciops.net>
date: Tue Aug 11 19:03:50 EDT 2020
add simple (and broken) descriptive statistics in awk
--- /dev/null
+++ b/descstat.awk
@@ -1,0 +1,110 @@
+#!/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]]++
+}