global sum sum2 n .
proc sd x . r .
   sum += x
   sum2 += x * x
   n += 1
   r = sqrt (sum2 / n - sum * sum / n / n)
.
v[] = [ 2 4 4 4 5 5 7 9 ]
for v in v[]
   sd v r
   print v & " " & r
.