Plotting Scatter & Bubble Charts From Text File

[sdawilson]

Morning all,

Firstly, thank you to wp for your support. I tried investigating your points this morning and I'm still lost.

This is driving me mad! I'm so close (see attached screen shot), I know it must be simple, but I just can't fix two things.

Background:
I'm writing an app to support a research project tracking carbon in infrastructure projects. The app reads a text file (output by MS Access, see attached) and plots either a bubble chart or a scatter chart and outputs the chart to an image file, which is then displayed in an Access image control. This plugs a huge hole in Access after the removal of Pivot Charts in Access 2013. The app has two command line arguments: the name of the text file containing the chart parameters and chart data, and the "/s" (silent) switch for "run and quit".

My first attempt was to use Excel as an embedded OLE object. Robust, pretty, but horribly, horribly slow... 26 - 28 seconds. I then wrote an app in Python using Matplotlib which worked perfectly, but it took 15 seconds to load and run. It was also a nightmare to distribute to the working group (42 local authorities in the UK). The Lazarus compiled app is elegant (as it creates a single, small distributable) and is very fast (as it runs and returns the chart image in under 2 seconds).

Problem
I posted my two problems last night (see attached screenshot):

1. The axes don't hold to the specified ranges, even where the datapoints are within those ranges (see attached jpeg).
2. The legend colour for scatter charts doesn't align with the colour on the chart.

These problems only relate to scatter charts (I think).

Confession
I've been coding in Pascal / Lazarus for a week, so I'm a super-newbie. My skills are in VB, VB.NET, and VBA (mostly in Excel and Project), so some of the principles are very familiar, others not-so-much. My limited Pascal skills are reflected in my coding style.

Code
I'll post my application code below and if anyone could help fix the issues, this would really help my research project.

Thank you for any support you could give me.

[sdawilson]

Here's the lfm:

Code: Pascal  [Select][+][-]

1. object Form1: TForm1
2.   Left = 963
3.   Height = 1722
4.   Top = 262
5.   Width = 1719
6.   Caption = 'Chart Script'
7.   ClientHeight = 1722
8.   ClientWidth = 1719
9.   DesignTimePPI = 240
10.   OnCreate = FormCreate
11.   OnDestroy = FormDestroy
12.   LCLVersion = '3.2.0.0'
13.   object tabDisplay: TPageControl
14.     Left = 16
15.     Height = 1608
16.     Top = 8
17.     Width = 1690
18.     ActivePage = tabChart
19.     Anchors = [akTop, akLeft, akRight, akBottom]
20.     TabIndex = 1
21.     TabOrder = 0
22.     object tabScript: TTabSheet
23.       Caption = 'Script'
24.       ClientHeight = 1536
25.       ClientWidth = 1670
26.       object grdScript: TStringGrid
27.         Left = 8
28.         Height = 1400
29.         Top = 128
30.         Width = 1650
31.         Anchors = [akTop, akLeft, akRight, akBottom]
32.         ColCount = 3
33.         ExtendedSelect = False
34.         Options = [goFixedVertLine, goFixedHorzLine, goVertLine, goHorzLine, goRangeSelect, goEditing, goSmoothScroll]
35.         RowCount = 1
36.         TabOrder = 0
37.         ColWidths = (
38.           389
39.           357
40.           584
41.         )
42.         Cells = (
43.           3
44.           0
45.           0
46.           'Section'
47.           1
48.           0
49.           'Property'
50.           2
51.           0
52.           'Setting'
53.         )
54.       end
55.       object cmbFiles: TComboBox
56.         Left = 8
57.         Height = 49
58.         Top = 64
59.         Width = 1650
60.         Anchors = [akTop, akLeft, akRight]
61.         ItemHeight = 41
62.         TabOrder = 1
63.         OnClick = cmbFilesClick
64.       end
65.       object Label1: TLabel
66.         Left = 8
67.         Height = 41
68.         Top = 16
69.         Width = 132
70.         Caption = 'File Name'
71.       end
72.     end
73.     object tabChart: TTabSheet
74.       Caption = 'Chart'
75.       ClientHeight = 1536
76.       ClientWidth = 1670
77.       object chtPlot: TChart
78.         Left = 8
79.         Height = 1520
80.         Top = 8
81.         Width = 1658
82.         AxisList = <        
83.           item
84.             Intervals.Count = 4
85.             Intervals.MaxLength = 0
86.             Intervals.MinLength = 0
87.             Intervals.Options = [aipUseCount]
88.             Marks.Format = '%0:.0f'
89.             Marks.LabelBrush.Style = bsClear
90.             Marks.Range.Max = 100
91.             Marks.Range.UseMax = True
92.             Marks.Range.UseMin = True
93.             Marks.Style = smsCustom
94.             Minors = <>
95.             Range.Max = 100
96.             Range.UseMax = True
97.             Range.UseMin = True
98.             Title.LabelFont.Orientation = 900
99.             Title.Visible = True
100.             Title.Caption = 'Y Axis'
101.             Title.LabelBrush.Style = bsClear
102.           end        
103.           item
104.             Intervals.Count = 10
105.             Intervals.MaxLength = 0
106.             Intervals.MinLength = 0
107.             Intervals.Options = [aipUseCount]
108.             Alignment = calBottom
109.             Marks.Format = '%0:.0f'
110.             Marks.LabelBrush.Style = bsClear
111.             Marks.Range.Max = 100
112.             Marks.Range.UseMax = True
113.             Marks.Range.UseMin = True
114.             Marks.Style = smsCustom
115.             Minors = <>
116.             Range.Max = 100
117.             Range.UseMax = True
118.             Range.UseMin = True
119.             Title.Visible = True
120.             Title.Caption = 'X Axis'
121.             Title.LabelBrush.Style = bsClear
122.           end>
123.         BackColor = clCream
124.         Extent.UseXMax = True
125.         Extent.UseXMin = True
126.         Extent.UseYMax = True
127.         Extent.UseYMin = True
128.         Extent.XMax = 100
129.         Extent.YMax = 100
130.         ExtentSizeLimit.UseXMax = True
131.         ExtentSizeLimit.UseXMin = True
132.         ExtentSizeLimit.UseYMax = True
133.         ExtentSizeLimit.UseYMin = True
134.         ExtentSizeLimit.XMax = 100
135.         ExtentSizeLimit.YMax = 100
136.         Legend.Visible = True
137.         Title.Font.CharSet = ANSI_CHARSET
138.         Title.Font.Height = -40
139.         Title.Font.Pitch = fpVariable
140.         Title.Font.Quality = fqDraft
141.         Title.Font.Style = [fsBold]
142.         Title.Text.Strings = (
143.           'Chart'
144.         )
145.         Title.Visible = True
146.         OnBeforeDrawBackWall = chtPlotBeforeDrawBackWall
147.         Anchors = [akTop, akLeft, akRight, akBottom]
148.         Color = clWhite
149.       end
150.     end
151.   end
152.   object cmdClose: TButton
153.     Left = 1518
154.     Height = 80
155.     Top = 1624
156.     Width = 188
157.     Anchors = [akRight, akBottom]
158.     Caption = 'Close'
159.     Color = 15912605
160.     Font.Style = [fsBold]
161.     ParentFont = False
162.     TabOrder = 1
163.     OnClick = cmdCloseClick
164.   end
165.   object cmdUpdate: TButton
166.     Left = 18
167.     Height = 80
168.     Top = 1624
169.     Width = 188
170.     Anchors = [akLeft, akBottom]
171.     Caption = 'Update'
172.     Color = 15912605
173.     Font.Style = [fsBold]
174.     ParentFont = False
175.     TabOrder = 2
176.     OnClick = cmdUpdateClick
177.   end
178. end

Here's my code:

Code: Pascal  [Select][+][-]

1. unit ReadScriptFile;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   LazUtils, StrUtils, FileUtil, TAGraph, TASeries, TAStyles, TATools, ]"]>BlockedltiSeries, Classes,
9.   SysUtils, Forms, Controls, Graphics, Dialogs, Grids, StdCtrls, ComCtrls, ValEdit, TACustomSeries, TASources,
10.   Types, TATypes, TACustomSource, TADrawUtils, TAChartUtils, TAChartAxisUtils;
11.  
12. type
13.  
14.   { TForm1 }
15.  
16.   TForm1 = class(TForm)
17.     chtPlot: TChart;
18.     cmdClose: TButton;
19.     cmdUpdate: TButton;
20.     cmbFiles: TComboBox;
21.     Label1: TLabel;
22.     grdScript: TStringGrid;
23.     tabDisplay: TPageControl;
24.     tabScript: TTabSheet;
25.     tabChart: TTabSheet;
26.     procedure chtPlotBeforeDrawBackWall(ASender: TChart; ACanvas: TCanvas;
27.       const ARect: TRect; var ADoDefaultDrawing: Boolean);
28.     procedure cmbFilesClick(Sender: TObject);
29.     procedure cmdCloseClick(Sender: TObject);
30.     procedure cmdUpdateClick(Sender: TObject);
31.     procedure FormCreate(Sender: TObject);
32.     procedure FormDestroy(Sender: TObject);
33.     procedure LoadFileBox(aFName: String);
34.     procedure SetAxisAttributes();
35.     procedure LoadScript();
36.     procedure ProcessScript();
37.     procedure PlotSeries();
38.     function ColorStrToColor(WebColor: string): TColor;
39.     function RGB(r, g, b: Byte): TColor;
40.   private
41.     FBackImage: TPicture;
42.   public
43.  
44.   end;
45.  
46. var
47.   Form1: TForm1; sChartTYpe: string; pPointerSize: integer;
48.   pMinX: double; pMaxX: double; pMinY: double; pMaxY: double; pStopsX: integer; pStopsY: integer;
49.  
50.  
51. implementation
52.  
53. {$R *.lfm}
54.  
55. { TForm1 }
56.  
57. procedure TForm1.FormCreate(Sender: TObject);
58. var
59.    pParam: string;
60.    pFile: string;
61. begin
62.   LoadFileBox('D:\Lazarus');
63.   If paramcount > 0 then
64.      cmbFiles.Text :=  paramstr(1);
65.      LoadScript;
66.      ProcessScript;
67.      If paramcount =2 then
68.         if lowercase(paramstr(2)) = '/s' then
69.            begin
70.            beep;
71.            close;
72.            halt(0);
73.            end
74. end;
75.  
76. procedure TForm1.FormDestroy(Sender: TObject);
77. begin
78.   FBackImage.Free;
79. end;
80.  
81. procedure TForm1.chtPlotBeforeDrawBackWall(ASender: TChart; ACanvas: TCanvas;
82.   const ARect: TRect; var ADoDefaultDrawing: Boolean);
83. begin
84.   ACanvas.StretchDraw(ARect, FBackImage.Graphic);
85.   ADoDefaultDrawing := false;
86. end;
87.  
88. procedure TForm1.cmbFilesClick(Sender: TObject);
89. begin
90.   LoadScript;
91. end;
92.  
93. procedure TForm1.cmdCloseClick(Sender: TObject);
94.   var
95.   pSelected: Integer;
96. begin
97.   // Show a confirmation dialog
98.   pSelected := MessageDlg('Are you sure?',mtConfirmation, mbOKCancel, 0);
99.  
100.   // Show the button type selected
101.   if pSelected = mrOK then Close;
102.  
103. end;
104.  
105. procedure TForm1.cmdUpdateClick(Sender: TObject);
106. begin
107.   ProcessScript;
108. end;
109.  
110. procedure TForm1.LoadFileBox(aFName: String);
111. var
112.   list: TStringList;
113. begin
114.   list := FindAllFiles(aFName, '*.txt' , False {don't search in subdirectory});
115.   cmbFiles.Items := list;
116.   list.Free;
117. end;
118.  
119. procedure Tform1.LoadScript();
120.  
121. var
122.   pFile: TextFile;
123.   pPath: string;
124.   pLine: string;
125.   pSection: string;
126.   pFunction: TStringArray;
127.   pRow: integer;
128. begin
129.   while grdScript.RowCount > 1 do
130.   begin
131.     grdScript.DeleteRow(1);
132.   end;
133.   //showmessage(pPath);
134.   pPath:= cmbFiles.Text;
135.   AssignFile(pFile, pPath);
136.    try
137.     // Open the file for reading
138.      reset(pFile);
139.     // Keep reading lines until the end of the file is reached
140.     //lstscript.Items.clear;
141.     while not eof(pFile) do
142.     begin
143.       readln(pFile, pLine);
144.       if Trim(pLine) <> '' then
145.         begin
146.         if pos(':',pLine)=0 then
147.            begin
148.              pSection := pLine;
149.             // pLine := pSection + #9 + '' + #9 + '';
150.             // lstScript.Items.Add(pLine);
151.            end;
152.         if pos(':',pLine)>0 then
153.            begin
154.              pFunction := pLine.Split(':');
155.              pRow := grdScript.RowCount;
156.              grdScript.RowCount := pRow + 1;
157.              grdScript.Cells[0, pRow] := trim(pSection);
158.              grdScript.Cells[1, pRow] := trim(pFunction[0]);
159.              grdScript.Cells[2, pRow] := trim(pFunction[1]);
160.              if high(pFunction)>1 then
161.                grdScript.Cells[2, pRow] := trim(pFunction[1]) + ':' + trim(pFunction[2]);
162.            end;
163.         end;
164.           // lstScript.Items.Add(pLine);
165.     end;
166.      // Done so close the file
167.      CloseFile(pFile);
168.    except
169.     on E: EInOutError do
170.     ShowMessage('File not found.');
171.   end;
172. end;
173.  
174. procedure Tform1.ProcessScript();
175. var
176.  pRow: integer;
177.  pRowCount: integer;
178.  pCol: integer;
179.  pSection: string;
180.  pProperty: string;
181.  pSetting: string;
182.  pAxis: integer;
183.  pFile: string;
184.  pFormat: string;
185. begin
186.   pRowCount := grdScript.RowCount - 1;
187.   for pRow := 1 to pRowCount do
188.   begin
189.     pSection := grdScript.Cells[0, pRow];
190.     pProperty := grdScript.Cells[1, pRow];
191.     pSetting := grdScript.Cells[2, pRow];
192.  
193.     //Chart...
194.     If lowercase(pSection) = 'chart' then
195.     begin
196.       If LowerCase(pProperty) = 'type' then sChartType := lowercase(pSetting);
197.       if LowerCase(pProperty) = 'save' then pFile := pSetting;
198.       if LowerCase(pProperty) = 'format' then pFormat := lowercase(pSetting);
199.       if LowerCase(pProperty) = 'pointer size' then pPointerSize := lowercase(pSetting).ToInteger;
200.       if LowerCase(pProperty) = 'background' then
201.         begin
202.             FBackImage := TPicture.Create;
203.             FBackImage.LoadFromFile(pSetting);
204.         end;
205.     end;
206.  
207.     //Title...
208.     If lowercase(pSection) = 'title' then
209.     begin
210.       if lowercase(pProperty) = 'text' then chtplot.Title.Text.Text := pSetting;
211.       if lowercase(pProperty) = 'size' then chtplot.Title.Font.Size := pSetting.ToInteger;
212.       if lowercase(pProperty) = 'bold' then
213.         If lowercase(pSetting) = 'true' then
214.           chtplot.Title.Font.Bold := true
215.         else
216.           chtplot.Title.Font.Bold := false;
217.       if LowerCase(pProperty) = 'color' then
218.         begin
219.           pSetting := UpperCase(pSetting);
220.           chtPlot.Title.Font.Color := ColorStrToColor(pSetting);
221.         end;
222.     end;
223.  
224.     //Set Axis...
225.     If Pos('axis',lowercase(pSection)) > 0 then
226.       case lowercase(pSection) of
227.         'xaxis': pAxis := 1;
228.         'yaxis': pAxis := 0;
229.       end
230.     else
231.       pAxis := -1;
232.  
233.     If pAxis >= 0 then
234.     begin
235.       chtPlot.Axislist[pAxis].Title.Distance := chtplot.Title.Font.Size + 30;
236.       if LowerCase(pProperty) = 'text' then chtPlot.Axislist[pAxis].Title.Caption := pSetting;
237.       if LowerCase(pProperty) = 'size' then chtPlot.Axislist[pAxis].LabelSize := pSetting.ToInteger;
238.       if LowerCase(pProperty) = 'color' then
239.         begin
240.           pSetting := UpperCase(pSetting);
241.           chtPlot.AxisList[pAxis].Title.LabelFont.Color := ColorStrToColor(pSetting);
242.         end;
243.  
244.       if LowerCase(pProperty) = 'min' then
245.         If pAxis = 0 then pMinY := pSetting.ToInteger else pMinX :=pSetting.ToInteger;
246.  
247.       if lowercase(pProperty) = 'max' then
248.           If pAxis = 0 then pMaxY := pSetting.ToInteger else pMaxX :=pSetting.ToInteger;
249.  
250.       if LowerCase(pProperty) = 'stops' then
251.           If pAxis = 0 then pStopsY := pSetting.ToInteger else pStopsX :=pSetting.ToInteger;
252.  
253.       if LowerCase(pProperty) = 'margin' then chtPlot.Axislist[pAxis].Title.Distance := chtplot.Title.Font.Size + psetting.ToInteger ;
254.  
255.       if LowerCase(pProperty) = 'bold' then
256.         If lowercase(pSetting) = 'true' then
257.           chtPlot.Axislist[pAxis].Title.LabelFont.Bold := true
258.         else
259.           chtPlot.Axislist[pAxis].Title.LabelFont.Bold := false;
260.     end;
261.   end;
262.  
263.   //Plot data...
264.  
265.   PlotSeries;
266.   SetAxisAttributes;
267.  
268.   //Save graphic file.
269.   if pFile<>'' then
270.     if (pFormat = 'jpeg') or (pFormat = 'jpg') then
271.       chtPlot.SaveToFile(TJPEGImage, pFile);
272.     if (pformat = 'bmp') or (pformat = 'bitmap') then
273.       chtPlot.SaveToFile(TBitmap, pFile);
274.     if (pformat = 'png') or (pformat = 'portable network graphic') then
275.       chtPlot.SaveToFile(TPortableNetworkGraphic, pFile);
276. end;
277.  
278. procedure Tform1.PlotSeries();
279. var
280.   pRow: integer;
281.   pRowCount: integer;
282.   pSeriesBP: TBubbleSeries;
283.   pSeriesXY: TLineSeries;
284.   pSeriesPtr: integer;
285.   pSection: string;
286.   pProperty: string;
287.   pSetting: string;
288.   pData: array of string;
289.   pX: Double;
290.   pY: Double;
291.   pR: Double;
292.   pPointer: string;
293.   pShape: integer;
294.   pColor: Tcolor;
295. //  pSeriesMarks: TseriesMarksStyle;
296. begin
297.   pRowCount := grdScript.RowCount - 1;
298.   pSeriesPtr :=1;
299.   chtPlot.ClearSeries;
300.   for pRow := 1 to pRowCount do
301.   begin
302.     pSection := LowerCase(grdScript.Cells[0, pRow]);
303.     pProperty := grdScript.Cells[1, pRow];
304.     pSetting := grdScript.Cells[2, pRow];
305.  
306.     //Bubble chart...
307.     If pSection = 'bubble series' then
308.       begin
309.         pSeriesBP := TBubbleSeries.Create(chtPlot);
310.         chtPlot.AddSeries(pSeriesBP);
311.         pData := pSetting.Split(',');
312.         pX := pData[0].ToDouble;
313.         pY := pData[1].ToDouble;
314.         pR := pData[2].ToDouble;
315.         If lowercase(pData[3]) = 'random' then
316.           pColor := (Random(256) * Random(256)) + Random(256)
317.         else
318.           pColor := ColorStrToColor(pData[3]);
319.  
320.         pSeriesBP.AddXY(pX, pY, pR,pProperty, pColor);
321.         pSeriesBP.BubbleBrush.Color:= pColor;
322.         pSeriesBP.Transparency:=60;
323.         If lowercase(pData[4]) = 'data_labels=true' then
324.           begin
325.             pSeriesBP.Marks.Format:= pProperty + ',' + pData[0] + ',' + pData[1] + ',' + pData[2];
326.             pSeriesBP.Marks.Visible := true;
327.           end;
328.         pSeriesBP.Name := pProperty;
329.         pSeriesBP.Title := pProperty;
330.         pSeriesBP.ShowInLegend:=true;
331.       end;
332.  
333.     //Scatter series...
334.     If pSection = 'scatter series' then
335.       begin
336.         pSeriesXY := TLineSeries.Create(chtPlot);
337.         chtPlot.AddSeries(pSeriesXY);
338.         pData := pSetting.Split(',');
339.         pX := pData[0].ToDouble;
340.         pY := pData[1].ToDouble;
341.         pPointer := lowercase(pData[2]);
342.  
343.         //Process colour...
344.         If lowercase(pData[3]) = 'random' then
345.           pColor := (Random(256) * Random(256)) + Random(256)
346.         else
347.           pColor := ColorStrToColor(pData[3]);
348.  
349.  
350.  
351.         // Process point data...
352.         pSeriesXY.AddXY(pX, pY, pProperty, pColor);
353.         pSeriesXY.ShowLines:= false;
354.         pSeriesXY.ShowPoints:=true;
355.         pSeriesXY.LinePen.Color := pColor;
356.         pSeriesXY.SeriesColor := pColor;
357.  
358.         If pPointerSize=0 then
359.           pPointerSize := 15;
360.  
361.         pSeriesXY.Pointer.HorizSize:=pPointerSize;
362.         pSeriesXY.Pointer.VertSize:=pPointerSize;
363.  
364.         // Process point shape...
365.         case pPointer of
366.           'cross': pSeriesXY.Pointer.Style := psCross;
367.           'circle': pSeriesXY.Pointer.Style:= psCircle;
368.           'diagcross': pSeriesXY.Pointer.Style := psDiagCross;
369.           'downtriangle': pSeriesXY.Pointer.Style := psDownTriangle;
370.           'triange': pSeriesXY.Pointer.Style := psTriangle;
371.           'star': pSeriesXY.Pointer.Style := psStar;
372.           'diamond': pSeriesXY.Pointer.Style := psDiamond;
373.           'lefttriangle': pSeriesXY.Pointer.Style := psLeftTriangle;
374.           'righttriangle': pSeriesXY.Pointer.Style := psRightTriangle;
375.           'vertbar': pSeriesXY.Pointer.Style := psVertBar;
376.           'horbar': pSeriesXY.Pointer.Style := psHorBar;
377.           'point': pSeriesXY.Pointer.Style := psPoint;
378.           'hexagon': pSeriesXY.Pointer.Style := psHexagon;
379.           'fullstar': pSeriesXY.Pointer.Style := psFullStar;
380.           'lowbracket': pSeriesXY.Pointer.Style := psLowBracket;
381.           'highbracket': pSeriesXY.Pointer.Style := psHighBracket;
382.           'leftbracket': pSeriesXY.Pointer.Style := psLeftBracket;
383.           'rightbracket': pSeriesXY.Pointer.Style := psRightBracket;
384.           'none': pSeriesXY.Pointer.Style := psNone;
385.         else
386.           pSeriesXY.Pointer.Style:= psCircle;
387.         end;
388.  
389.         pSeriesXY.Transparency:=30;
390.         If lowercase(pData[4]) = 'data_labels=true' then
391.           begin
392.             pSeriesXY.Marks.Format:= pProperty + ',' + pData[0] + ',' + pData[1];
393.             pSeriesXY.Marks.Visible := true;
394.           end;
395.         pSeriesXY.Name := pProperty;
396.         pSeriesXY.Title := pProperty;
397.         pSeriesXY.ShowInLegend:=true;
398.       end;
399.     end;
400. end;
401.  
402. procedure Tform1.SetAxisAttributes();
403. begin
404.  
405.   // 'xaxis': pAxis := 1;
406.   // 'yaxis': pAxis := 0;
407.  
408.   chtPlot.Axislist[0].Range.Min := pMinY;
409.   chtPlot.AxisList[0].Range.Max := pMaxY;
410.   chtPlot.Axislist[0].Marks.Range.Min := pMinY;
411.   chtPlot.Axislist[0].Marks.Range.Max := pMaxY;
412.   chtPlot.Axislist[0].Intervals.Count := pStopsY;
413.  
414.   chtPlot.Axislist[1].Range.Min := pMinX;
415.   chtPlot.AxisList[1].Range.Max := pMaxX;
416.   chtPlot.Axislist[1].Marks.Range.Min := pMinX;
417.   chtPlot.Axislist[1].Marks.Range.Max := pMaxX;
418.   chtPlot.Axislist[1].Intervals.Count := pStopsX;
419.  
420.   chtPlot.Extent.YMax := pMaxY;
421.   chtPlot.Extent.YMin := pMinY;
422.   chtPlot.Extent.XMax := pMaxX;
423.   chtPlot.Extent.XMin := pMinX;
424.   chtPlot.Extent.UseXMax := true;
425.   chtPlot.Extent.UseXMin := true;
426.   chtPlot.Extent.UseYMax := true;
427.   chtPlot.Extent.UseYMin := true;
428.  
429.   chtPlot.ExtentSizeLimit.YMax := pMaxY;
430.   chtPlot.ExtentSizeLimit.YMin := pMinY;
431.   chtPlot.ExtentSizeLimit.XMax := pMaxX;
432.   chtPlot.ExtentSizeLimit.XMin := pMinX;
433.   chtPlot.ExtentSizeLimit.UseXMax := true;
434.   chtPlot.ExtentSizeLimit.UseXMin := true;
435.   chtPlot.ExtentSizeLimit.UseYMax := true;
436.   chtPlot.ExtentSizeLimit.UseYMin := true;
437.  
438. end;
439.  
440. function TForm1.RGB(r, g, b: Byte): TColor;
441. begin
442.   Result := (Integer(r) or (Integer(g) shl 8) or (Integer(b) shl 16));
443. end;
444.  
445. function TForm1.ColorStrToColor(WebColor: string): TColor;
446. begin
447.   Result :=
448.     RGB(
449.       StrToInt('$' + Copy(WebColor, 2, 2)),
450.       StrToInt('$' + Copy(WebColor, 4, 2)),
451.       StrToInt('$' + Copy(WebColor, 6, 2)));
452. end;
453.  
454. end.
455.  

[wp]

The space in the chart above y=100 is caused by the fact that you want the series to display data point labels. The chart here is rather dumb, and just makes sure that there is space available for the label of the data point with largest y value - it does not "know" that there is plenty of space left because the axis limits are fixed by means of the Range property. The only thing you could do is to switch the series.MarkPositions to lmpInside - this means that the labels are drawn "inside" the area convered by the data values. Since now there definitely is space for all labels, there is no need to expand the axis limits. But you have no control of whether the label is drawn above or below the data point - I forgot the algorithm how this is decided, and the situation here is even more complicated because the axis limit are frozen by means of the chart's Extent property.

[sdawilson]

Bingo! Excellent, thanks wp!!! That fixes the problem with the chart scales.

Did you have any further thoughts / guidance regarding the colour of the legend items?

[wp]

Sorry, I forgot...

Add the following code to where pSeriesXY is created, and add unit TALegend to "uses":

Code: Pascal  [Select][+][-]

1.         pSeriesXY.Legend.Multiplicity := lmPoint;

BTW, this kind of makes the series labels obsolete, which also fixes the "space above y=100" issue.

[sdawilson]

wp, you truly are a hero! It worked first time!

You're right about the label negating the need for the legend, but I wanted to give the option of one or the other, or both. Academics are fanatical about things like that.

I really love Lazarus and the charting is amazing... although a little complicated for us newbies. This little bit of code fixes main charting shortfall in MS Access. I'll move on to adding labelled pie charts later (another irritating shortfall)... but for now, thank you very much!

[wp]

I'll move on to adding labelled pie charts later (another irritating shortfall)... but for now, thank you very much!

There are some demos on pie series in the (lazarus)/components/tachart/demo folders.

[sdawilson]

It was all going so well and then I got an "Access Violation". I have no idea how this happened... or what it is.

wp, if you're still around, can you help? I've attached the reported error.

[wp]

"Access violation" usually means: "you're accessing an object which does not exist". So, did you create the FBackImage, and has some image file been loaded into it so that FBackImage.Graphic exists, too? (Not sure about the second condition, though). Put a breakpoint at the offending line ("ACanvas.Stretchdraw(...)"), run the application; when it stops at the breakpoint, move the mouse over the word "FBackImage" --> the popup hint tells you whether the variable is nil. If it is, it may help to check for nil before accessing it:

Code: Pascal  [Select][+][-]

1. if (FBackImage <> nil) and (FBackImage.Graphic <> nil) then
2.   ACanvas.StretchDraw(ARect, FBackImage.Graphic);