MODULE DiversPredict;
(* Diversity prediction theorem *)

FROM STextIO IMPORT
  WriteLn, WriteString;
FROM SRealIO IMPORT
  WriteFixed;

TYPE
  TEstims = ARRAY [0 .. 1], [0 .. 4] OF REAL;
VAR
  Estims: TEstims;
  TrueVal, Sum, AvgErr, Avg, CrowdErr, Diff: REAL;
  I, J: CARDINAL;
BEGIN
  Estims := TEstims{{48.0, 47.0, 51.0, 0.0, 0.0},
                    {48.0, 47.0, 51.0, 42.0, 0.0}};
  TrueVal := 49.0;
  FOR I := 0 TO 1 DO
    Sum := 0.0;
    J := 0;
    WHILE Estims[I, J] <> 0.0 DO
      Diff := Estims[I, J] - TrueVal;
      Sum := Sum + Diff * Diff;
      J := J + 1;
    END;
    AvgErr := Sum / FLOAT(J);
    WriteString("Average error: ");
    WriteFixed(AvgErr, 3, 7);
    WriteLn;
    Sum := 0.0;
    J := 0;
    WHILE Estims[I, J] <> 0.0 DO
      Sum := Sum + Estims[I, J];
      J := J + 1;
    END;
    Avg := Sum / FLOAT(J);
    Diff := TrueVal - Avg;
    CrowdErr := Diff * Diff;
    WriteString("Crowd error  : ");
    WriteFixed(CrowdErr, 3, 7);
    WriteLn;
    WriteString("Diversity    : ");
    WriteFixed(AvgErr - CrowdErr, 3, 7);
    WriteLn;
    WriteLn;
  END;
END DiversPredict.