lazarus-ccr/applications/lazstats/source/forms/analysis/nonparametric/binomialunit.pas

unit BinomialUnit;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, StdCtrls, ExtCtrls,
  FunctionsLib, GraphLib, BasicStatsReportAndChartFormUnit;

type

  { TBinomialForm }

  TBinomialForm = class(TBasicStatsReportAndChartForm)
    FreqAEdit: TEdit;
    FreqBEdit: TEdit;
    PropAEdit: TEdit;
    FreqALabel: TLabel;
    FreqBLabel: TLabel;
    PropALabel: TLabel;
  private
	
  protected
    procedure AdjustConstraints; override;
    procedure Compute; override;
    function Validate(out AMsg: String; out AControl: TWinControl): Boolean; override;

  public
    constructor Create(AOwner: TComponent); override;
    procedure Reset; override;
  end; 

var
  BinomialForm: TBinomialForm;


implementation

{$R *.lfm}

uses
  Math,
  TACustomSeries,
  Globals, MathUnit, ChartFrameUnit;

{ TBinomialForm }

constructor TBinomialForm.Create(AOwner: TComponent);
begin
  inherited;
  FChartFrame.Chart.Margins.Bottom := 0;
  FChartFrame.Chart.BottomAxis.AxisPen.Visible := true;
  FChartFrame.Chart.BottomAxis.ZPosition := 1;
end;

	
procedure TBinomialForm.AdjustConstraints;
begin
  inherited;

  ParamsPanel.Constraints.MinWidth := Max(
    PropALabel.Width + PropAEdit.Width + PropAEdit.BorderSpacing.Left,
    4*CloseBtn.Width + 3*CloseBtn.BorderSpacing.Left
  );
  ParamsPanel.Constraints.MinHeight := PropAEdit.Top + PropAEdit.Height
end;


procedure TBinomialForm.Reset;
begin
  inherited;
  FreqAEdit.Clear;
  FreqBEdit.Clear;
  PropAEdit.Clear;
end;


procedure TBinomialForm.Compute;
const
  N_MAX = 35;
var
  P, Q, probability, z, correctedA, SumProb, mean, sigma: double;
  A, B, N, i: integer;
  xPts: DblDyneVec = nil;
  yPts: DblDyneVec = nil;
  lReport: TStrings;
  ser: TChartSeries;
begin
  A := round(StrToFloat(FreqAEdit.Text));
  B := round(StrToFloat(FreqBEdit.Text));
  P := StrToFloat(PropAEdit.Text);
  N := A + B;
  Q := 1.0 - P;

  lReport := TStringList.Create;
  try
    lReport.Add('BINOMIAL PROBABILITY TEST');
    lReport.Add('');
    lReport.Add('Frequency of %d out of %d observed', [A, N]);
    lReport.Add('The theoretical proportion expected in category A is %.3f', [P]);
    lReport.Add('');
    lReport.Add('The test is for the probability of a value in category A as small or smaller');
    lReport.Add('than that observed given the expected proportion.');
    lReport.Add('');

    if (N > N_MAX) then
    begin
      // Use normal distribution approximation
      correctedA := A;
      if A < N * P then correctedA := A + 0.5;
      if A > N * P then correctedA := A - 0.5;
      z := (correctedA - N * P) / sqrt(N * P * Q);
      lReport.Add('Z value for normal nistribution approximation: %.3f', [z]);
      Probability := NormalDist(z);
      lReport.Add('Probability: %6.4f', [Probability]);
    end else
    begin
      // Use binomial fomula
      sumProb := 0;
      for i := 0 to A do
      begin
        Probability := combos(i, N) * IntPower(P, i) * IntPower(Q, N-i);
        lReport.Add('Probability of %d: %6.4f', [i, Probability]);
        sumProb := sumProb + Probability;
      end;
      lReport.Add('');
      lReport.Add('Binomial Probability of %d or less out of %d: %.4f', [A, N, sumProb]);
    end;

    FReportFrame.DisplayReport(lReport);
  finally
    lReport.Free;
  end;

  // Plot the distribution
  FChartFrame.Clear;
  FChartFrame.SetXTitle('Values');
  FChartFrame.SetYTitle('Probability');
  if N > N_MAX then
  begin
    FChartFrame.SetTitle('Binomial Distribution' + LineEnding + '(approximated by Normal Distribution)');
    mean := N*P;
    sigma := sqrt(N * P * Q);
    SetLength(xPts, N+1);
    SetLength(yPts, N+1);
    for i := 0 to N do
    begin
      xPts[i] := i;
      yPts[i] := NormalDistDensity(i, mean, sigma);
    end;
  end else
  begin
    FChartFrame.SetTitle('Binomial Distribution');
    SetLength(xPts, N+1);
    SetLength(yPts, N+1);
    for i := 0 to N do
    begin
      xPts[i] := i;
      yPts[i] := Combos(i, N) * IntPower(p, i) * IntPower(Q, N-i);
    end;
  end;
  if N < 50 then
    ser := FChartFrame.PlotXY(ptBars, xPts, yPts, nil, nil, '', DATA_COLORS[0])
  else
    ser := FChartFrame.PlotXY(ptArea, xPts, yPts, nil, nil, '', DATA_COLORS[0]);
  ser.ZPosition := 2;
  FChartFrame.Chart.Legend.Visible := false;
end;


function TBinomialForm.Validate(out AMsg: String; out AControl: TWinControl): Boolean;
var
  x: Double;
  n: Integer;
begin
  Result := false;
  if (FreqAEdit.Text = '') or (FreqBEdit.Text = '') or (PropAEdit.Text = '') then
  begin
    AMsg := 'Value not specified.';
    if FreqAEdit.Text = '' then AControl := FreqAEdit;
    if FreqBEdit.Text = '' then AControl := FreqBEdit;
    if PropAEdit.Text = '' then AControl := PropAEdit;
    exit;
  end;
  if not TryStrToInt(FreqAEdit.Text, n) then
  begin
    AMsg := 'No valid integer.';
    AControl := FreqAEdit;
    exit;
  end;
  if not TryStrToInt(FreqBEdit.Text, n) then
  begin
    AMsg := 'No valid integer.';
    AControl := FreqBEdit;
    exit;
  end;
  if not TryStrToFloat(PropAEdit.Text, x) then
  begin
    AMsg := 'No valid number.';
    AControl := PropAEdit;
    exit;
  end;
  if (x < 0) or (x > 1) then
  begin
    AMsg := 'Number between 0 and 1 expected.';
    AControl := PropAEdit;
    exit;
  end;

  Result := true;
end;

end.