Problem Statement

Write a stateful function, class, generator or co-routine that takes a series of floating point numbers, one at a time, and returns the running standard deviation of the series. The task implementation should use the most natural programming style of those listed for the function in the implementation language; the task must state which is being used. Do not apply Bessel's correction; the returned standard deviation should always be computed as if the sample seen so far is the entire population.

Use this to compute the standard deviation of this demonstration set,

{ 2 , 4 , 4 , 4 , 5 , 5 , 7 , 9 }

{\displaystyle {2,4,4,4,5,5,7,9}}

, which is

2

{\displaystyle 2}

.

Let's start with the solution:

;Define our Standard deviation function
Declare.d Standard_deviation(x)

; Main program
If OpenConsole()
  Define i, x
  Restore MyList
  For i=1 To 8
    Read.i x
    PrintN(StrD(Standard_deviation(x)))
  Next i
  Print(#CRLF$+"Press ENTER to exit"): Input()
EndIf

;Calculation procedure, with memory
Procedure.d Standard_deviation(In)
  Static in_summa, antal
  Static in_kvadrater.q
  in_summa+in
  in_kvadrater+in*in
  antal+1
  ProcedureReturn Pow((in_kvadrater/antal)-Pow(in_summa/antal,2),0.50)
EndProcedure

;data section
DataSection
MyList:
  Data.i  2,4,4,4,5,5,7,9
EndDataSection