You should create series for each date manually. So you should iterate your dataset, each time when you meet new date you should create new series, add it to the chart, and add values.
In case your dataset is not sorted you might use temporary Dictionary (TDcitionary<integer, TLineSeries> from Generics.Collections)to store series references.
DateTime value actually is a double where int part represents day. So you have own key for each date. Also you can assign it series Tag property for possible further use.
Use BeginUpdate() and EndUpdate() methods before and after populating series values.
When you create series use Chart reference as an owner. Next time you clear all series in chart, they will sucesfully destroyed.
Here is an example code:
procedure TForm7.UpdateSeries();
var sd : TDictionary<integer, TLineSeries>;
s : TLineSeries;
d : TDate;
dInt : integer;
x : double;
xlabel : string;
i : integer;
begin
DataChart.SeriesList.Clear();
sd := TDictionary<integer, TLineSeries>.Create();
try
while not query.eof do begin
d := query.FieldByName('Date').AsDateTime;
dInt := round(d);
if not sd.ContainsKey(dInt) then begin
s := TLineSeries.Create(DataChart);
s.Tag := dInt; {for further use}
DataChart.AddSeries(s);
s.ParentChart := DataChart;
s.Title := DateToStr(query.FieldByName('date').AsDateTime);
s.Color := Random($FFFFFF);
s.BeginUpdate();
sd.AddOrSetValue(dInt, s);
end
else s := sd[dInt];
//x value and label
x := query.FieldByName('time').AsDateTime;
xlabel := Format('Label %f', [x]);
s.AddXY(x, query.FieldByName('score').AsInteger, xlabel);
query.Next();
end;
finally
for i := 0 to DataChart.SeriesCount - 1 do begin
DataChart.Series[i].EndUpdate();
end;
sd.Free();
end;
end;
as question targets Delphi-7, it does not know about generics. So in this case the easiest way is to sort dataset by date (ORDER BY date). And then each time you meet new date, you should create new series. At first you need to initialize dInt := 0, and then compare it to FieldByName('date'). If it has changed, you should create new series.
dInt := 0;
try
while not query.eof do begin
d := query.FieldByName('Date').AsDateTime;
if round(d) <> dInt then begin
dInt := round(d);
s := TLineSeries.Create(DataChart);
....
