Data commit

Task/Cumulative-standard-deviation/OoRexx/cumulative-standard-deviation.rexx

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+sdacc = .SDAccum~new
+x = .array~of(2,4,4,4,5,5,7,9)
+sd = 0
+do i = 1 to x~size
+   sd = sdacc~value(x[i])
+   Say '#'i 'value =' x[i] 'stdev =' sd
+end
+
+::class SDAccum
+::method sum attribute
+::method sum2 attribute
+::method count attribute
+::method init
+  self~sum = 0.0
+  self~sum2 = 0.0
+  self~count = 0
+::method value
+  expose sum sum2 count
+  parse arg x
+  sum = sum + x
+  sum2 = sum2 + x*x
+  count = count + 1
+  return self~stddev
+::method mean
+  expose sum count
+  return sum/count
+::method variance
+  expose sum2  count
+  m = self~mean
+  return sum2/count - m*m
+::method stddev
+  return self~sqrt(self~variance)
+::method sqrt
+  arg n
+  if n = 0 then return 0
+  ans = n / 2
+  prev = n
+  do until prev = ans
+    prev = ans
+    ans = ( prev + ( n / prev ) ) / 2
+  end
+  return ans