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TAChart: Workaround for the derivative calculation at the first data point

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git-svn-id: trunk@32204 -
This commit is contained in:
ask 2011-09-07 09:36:25 +00:00
parent 3563b6e636
commit 643751d975
1 changed files with 14 additions and 9 deletions
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23
components/tachart/tasources.pas
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@ -176,7 +176,7 @@ type
FYOrder: array of Integer;
procedure CalcAccumulation(AIndex: Integer);
procedure CalcDerivative(AIndex: Integer);
procedure CalcDerivative(var AIndex: Integer);
procedure CalcPercentage;
procedure Changed(ASender: TObject);
procedure ExtractItem(out AItem: TChartDataItem; AIndex: Integer);
@ -859,12 +859,12 @@ begin
camDerivative:
CalcDerivative(AIndex);
end;
FIndex := AIndex;
end;
// Derivative is approximated by backwards finite difference
// with accuracy order of (AccumulationRange - 1).
procedure TCalculatedChartSource.CalcDerivative(AIndex: Integer);
procedure TCalculatedChartSource.CalcDerivative(var AIndex: Integer);
const
COEFFS: array [2..7, 0..6] of Double = (
( 1, -1, 0, 0, 0, 0, 0),
@ -877,14 +877,20 @@ var
prevItem: PChartDataItem;
i, j, ar: Integer;
dx: Double;
t: TChartDataItem;
begin
if AIndex = 0 then begin
AIndex := 1;
ExtractItem(t, AIndex);
FHistory.AddLast(t);
dx := t.X - FHistory.GetPLast(1)^.X;
end
else
dx := FItem.X - FHistory.GetPLast(1)^.X;
FItem.ClearY;
if AIndex = 0 then exit;
dx := FItem.X - FHistory.GetPLast(1)^.X;
if dx = 0 then exit;
ar := Min(AccumulationRange, AIndex);
if (ar = 0) or (ar > High(COEFFS)) then
ar := High(COEFFS);
ar := IfThen(AccumulationRange = 0, MaxInt, AccumulationRange);
ar := MinValue([ar, AIndex + 1, High(COEFFS)]);
for j := 0 to ar - 1 do begin
prevItem := FHistory.GetPLast(j);
FItem.Y += prevItem^.Y * COEFFS[ar, j];
@ -969,7 +975,6 @@ begin
else
CalcAccumulation(AIndex);
CalcPercentage;
FIndex := AIndex;
end;
function TCalculatedChartSource.IsSorted: Boolean;