How to plot points with label according to a specific field
lazarus / 39-Graphics

----------------------------------------------------------------------
Emmanuel · 2013-09-30 17:36

Now I know better how to use chart component !!!  Thank you ! , I just
hava a problem now with labels, I already  plot points on the graph
according to my table and X, Y fields, but I want also to show with
labels a specific field of my table, can you explain me how to do it ?


Thank you

----------------------------------------------------------------------
wp · 2013-09-30 18:38

Have look at the other tutorials
(http://wiki.lazarus.freepascal.org/Category:TAChart).

http://wiki.lazarus.freepascal.org/TAChart_Tutorial:_ListChartSource,_
Logarithmic_Axis,_Fitting, for example, shows how to add labels to
each data point. In this tutorial, however, data are entered at
designtime; the usual way is by applying the Add method of the series
or ChartSource. There are several overloaded versions of this method,
one of the optional parameters defines the label assigned to the data
point.

Here's an example how you could catch the data from a database table
or query and pass them to a series:

Code: [Select]var
  Dataset: TDataset;
  xField: TField;
  yField: TField;
  labelField: TField;
begin
  Chart1LineSeries1.Clear;
  Dataset.Open; 
  xField := Dataset.FieldByName('x values');
  yField := Dataset. FieldByName('y values');
  labelField := Dataset.FieldByName('data labels');
  while not Dataset.EoF do begin
    Chart1LineSeries1.AddXY(xField.AsFloat, yField.AsFloat,
labelField.AsString);
    Dataset.Next;
  end;
end;

Alternatively you can also use a DBChartSource which you can link to
your database fields on the one side, and to the series on the other
side.