correl.txt

《Delphi常用数值算法集》的配书源码

Procedure CORREL(DATA1,DATA2:array of real;N:integer;var ANS:array of real);
var
    FFT:array[0..128] of real;
    NO2,I:integer;  DUM,DUM1,DUM2:real;
begin
    TWOFFT(DATA1, DATA2, FFT, ANS, N);
    NO2:=N div 2;
    For I:=1 To NO2 + 1 do
    begin
      DUM:=ANS[2 * I - 1];
      DUM1:=FFT[2 * I - 1] * DUM + FFT[2 * I] * ANS[2 * I];
      ANS[2 * I - 1]:=DUM1 / NO2;
      DUM2:=FFT[2 * I] * DUM - FFT[2 * I - 1] * ANS[2 * I];
      ANS[2 * I]:=DUM2 / NO2;
    end;
    ANS[2]:=ANS[N + 1];
    REALFT(ANS, NO2, -1);
end;