LineSeries Null values

[daniele_h]

Dear all,
I'm trying to import data from a tab-separated file to a LineSeries by code (Delphi).
Unfortunately there are many gaps (blanks/null value) so that an error occurs ("not a valid floating point value") and tha data is not imported.
I tried to use TreatNulls:=tnSkip or tnIgnore, but to no avail.

What am I donig wrong ? I'm using following code.

Code: Select all

  ts := TSeriesTextSource.Create(Self);
  with ts do
  begin
    Fields.Clear;
    AddField('X',x);
    AddField('Y',y);
    HeaderLines := r;
    FieldSeparator := dm;
    DecimalSeparator := c;
    FileName := fn;

    ls := TLineSeries.Create(Self);
    with ls do
    begin
      ParentChart:= ch;
      DataSource := ts;
     // TreatNulls := tnSkip;
      ValueFormat:= la;

      XValues.DateTime:= True;
      ch.Axes.Bottom.DateTimeFormat := 'dd.mm.yyyy.hh:mm:ss.zzz'; 
      ch.Axes.Bottom.LabelsAngle:= 90;
      ch.Axes.Bottom.Increment:=DateTimeStep[dtOneMinute];
      Title := si;
    end;
    Active := True;
  end;
  except
    on E: EConvertError do
    begin
      Screen.Cursor := crDefault;
      ls.Free;
      raise Exception.Create(E.Message);
    end;
  end;

kind regards
Daniele

[Yeray]

Hi Daniele,

Thanks for the code but there are many variables that we can't see their values, and we can't see the database that you are using. It would be better if you could attach here a simple example project we can run as-is to reproduce the problem here.

[daniele_h]

Hi Yeray,

I was afraid you would say that it was not possible in the first place !

I'm a bit reluctant to post the whole project, but will prepare a "demo".
meanwhile, I understand your concerns about the the variables, so below find the code without variables.
I omitted to do this in the first place because I debugged enough to know it is indeed the problem of nil values. I'm not using a database dut reading from file.

Code: Select all

  ts := TSeriesTextSource.Create(Self);
  with ts do
  begin
    Fields.Clear;
    AddField('X',1);
    AddField('Y',1);
    HeaderLines := 1;
    FieldSeparator := #9;
    DecimalSeparator := chr(46);
    FileName := 'C:\TEMP\TabSeparated.txt';

    ls := TLineSeries.Create(Self);
    with ls do
    begin
      ParentChart:= chart1;
      DataSource := ts;
     // TreatNulls := tnSkip/tnIgnore; ??? <-- don't work either
      ValueFormat:= '0.00e-00';

      XValues.DateTime:= True;
      chart1.Axes.Bottom.DateTimeFormat := 'dd.mm.yyyy.hh:mm:ss.zzz';
      chart1.Axes.Bottom.LabelsAngle:= 90;
      chart1.Axes.Bottom.Increment:=DateTimeStep[dtOneMinute];
      Title := 'TestLine1';
    end;
    Active := True;
  end;
  except
    on E: EConvertError do
    begin
      Screen.Cursor := crDefault;
      ls.Free;
      raise Exception.Create(E.Message);
    end;
  end;

[daniele_h]

Dear Yeray,

Please find attached a demo of the problem. (Delphi 2007, Tchart Pro v8).
In the folder you find the file "TabSeparated.txt" which is imported on "FormCreate".
You will notice the blank value (ie. 4.4). Data is imported only until the missing value.
I would expect it to continue importing with the directive "TreatNulls:=tnSkip" until the end of the file.

Kind regards
daniele

[Yeray]

Hi Daniele,

Thanks for the project, now we understand better what you are trying to do.

Null values in a database must be customly handled as almost everybody marks them in a different way and also everybody wants to treat them in a different way. So you should loop through your datasource and when a null value is identified, you should manually add it to the series using the AddNull methods provided.

[daniele_h]

Hi Yeray,
I don't quite understand how I should accomplish what you are suggesting - and where/how else the "TreatNulls:=tnSkip/ignore" comes into play.
Would you be able to provide me with an example on how I should modify my code for the example I posted? I would really appreciate that.
thanks
daniele

[Yeray]

Hi Daniele,

Change your button1 code for the following to see an example:

Code: Select all

procedure TForm1.Button1Click(Sender: TObject);
var
   myFile : TextFile;
   text, tmpValueText   : string;
   i, FieldNum : Integer;
   XValue: TDateTime;
   YValue: Double;
   IsNull: Boolean;
begin
  ls := TLineSeries.Create(Self);
  with ls do
  begin
    ParentChart			:= chart1;
    ValueFormat			:= '0.00e-00';
//    TreatNulls      := tnSkip; // (tnDontPaint, tnSkip, tnIgnore)
    XValues.DateTime:= True;
    Title := 'TestLine1';
  end;

  DecimalSeparator 	:= chr(46);
  DateSeparator     := '.';

  AssignFile(myFile, 'TabSeparated.txt');
  Reset(myFile);

  ReadLn(myFile, text); //we skip the first 'header' line

  while not Eof(myFile) do
  begin
    ReadLn(myFile, text);
    FieldNum := 1;
    tmpValueText := '';
    IsNull := false;

    for i := 1 to length(text)-1 do
    begin
      if (text[i] = #9) then
      begin
        case FieldNum of
          1: XValue := StrToDateTime(tmpValueText);
          3: if (tmpValueText = '') then IsNull := true
             else YValue := StrToFloat(tmpValueText);
        end;
        FieldNum := FieldNum + 1;
        tmpValueText := '';
      end
      else tmpValueText := tmpValueText + text[i];

      if (i = length(text)-1) then
      begin
        if IsNull then ls.AddNullXY(XValue, 0)
        else ls.AddXY(XValue, YValue);
        IsNull := false;
      end;
    end;
  end;

  CloseFile(myFile);
end;

[daniele_h]

Dear Yeray,

You saved my day ! Works like a charm. Thank you so much

Cheers
Daniele