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git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@7925 8e941d3f-bd1b-0410-a28a-d453659cc2b4
65 lines
1.4 KiB
ObjectPascal
65 lines
1.4 KiB
ObjectPascal
program Project1;
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uses
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SysUtils,
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spe,
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MathUnit;
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// Numerical recipes
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function GammaLn(x: double): Double;
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{ gibt den Log der vollständigen Gamma-Funktion zurück (x>0).
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Gamma(x) = integral ( t^(x-1) * exp(-t) dt ) (von 0 bis Unendlich)
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(Log, um Floating Point Underflow zu vermeiden). }
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const
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stp = 2.50662827465;
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var
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xx,tmp,ser : extended;
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begin
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if x<=0 then
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raise Exception.Create('Argument für GammaLn ist negativ.');
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if (x > 1) then begin
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xx := x - 1.0;
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tmp := xx + 5.5;
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tmp := (xx+0.5) * ln(tmp) - tmp;
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ser := 1.0 + 76.18009173 /(xx+1.0) - 86.50532033/(xx+2.0)
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+ 24.01409822 /(xx+3.0) - 1.231739516/(xx+4.0)
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+ 0.120858003E-2/(xx+5.0) - 0.536382E-5/(xx+6.0);
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result := tmp + ln(stp*ser);
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end else
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if (x < 1) then
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result := GammaLn(x+1.0) - ln(x)
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else
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if (x=1) then
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result := 0.0;
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end;
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const
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xmin = 1e-3;
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xmax = 5.0;
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procedure Test;
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var
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i: Integer;
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x, y_lazStats, y_numlib, y_numrecip: Double;
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begin
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WriteLn('x':20, 'y(lazstats)':20, 'y(numlib)':20, 'y(Num.Recipies)':20);
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x := xmin;
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while (x <= xmax) do begin
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y_numlib := 1.0 - spelga(x);
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y_lazstats := MathUnit.gammaln(x);
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y_numrecip := gammaln(x);
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WriteLn(x:20:6, y_lazstats:20:5, y_numlib:20:5, y_numrecip:20:5);
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x := x*1.25
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// x := x + dx;
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end;
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end;
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begin
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WriteLn('GammaLn function');
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WriteLn;
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Test;
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ReadLn;
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end.
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