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    MeanAndStdDev

    Return mean and standard deviation of array.

    Declaration

    Source position: math.pp line 839

    procedure MeanAndStdDev(const data: Array of Single; var mean: Float; 
                       var stddev: Float);

    procedure MeanAndStdDev(const data: PSingle; const N: LongInt; 
                       var mean: Float; var stddev: Float);

    procedure MeanAndStdDev(const data: Array of Double; var mean: Float; 
                       var stddev: Float);

    procedure MeanAndStdDev(const data: PDouble; const N: LongInt; 
                       var mean: Float; var stddev: Float);

    procedure MeanAndStdDev(const data: Array of Extended; var mean: Float; 
                       var stddev: Float);

    procedure MeanAndStdDev(const data: PExtended; const N: LongInt; 
                       var mean: Float; var stddev: Float);

    Description

    meanandstddev calculates the mean and standard deviation of data and returns the result in mean and stddev, respectively. Stddev is zero if there is only one value. The second form accepts a pointer to an array of N values.

    Errors

    None.

    See also

    Name Description
    mean Return mean value of array.
    sum Return sum of values.
    sumofsquares Return sum of squares of values.
    momentskewkurtosis Return 4 first moments of distribution.

    Example

    Program Example28;

{ Program to demonstrate the Meanandstddev function. }
{ @ should return typed pointer }
{$T+}

Uses math;

Type
  TExArray = Array[1..100] of Extended;

Var
  I : Integer;
  ExArray : TExArray;
  Mean,stddev : Extended;

begin
  Randomize;
  for I:=low(ExArray) to high(ExArray) do
    ExArray[i]:=(Random-Random)*100;
  MeanAndStdDev(ExArray,Mean,StdDev);
  Writeln('Mean       : ',Mean:8:4);
  Writeln('StdDev     : ',StdDev:8:4);
  MeanAndStdDev(@ExArray[1],100,Mean,StdDev);
  Writeln('Mean   (b) : ',Mean:8:4);
  Writeln('StdDev (b) : ',StdDev:8:4);
end.