Ok this the good response,

do have a code Delphi with example, please
for the speed practice.

And if in chart ago a TGanttSeries, i hope retreive
0 or 1 as value ???

And if in chart ago a TLineSeries, i hope retreive
Y value

Please, i don't all anderstand with linear function

this is very sample, but perhaps difficult to do

I hope Obtain all Y value of the all series for
one value X (reference) , without click on chart but
with search in Serie[N].Xvalue

ex: for each Xvalue of the serie N, how what Yvalue to correspond for all series ??

My english is very Bad (speak french)
I try explain again.

I hope Obtain all value of the all series for
one value X (reference) , without click on chart but
with Serie[x].Xvalue

ex: for each Xvalue of the serie 1, how what Yvalue to correspond for all series ??

Hello How know the other series values from the first serie with the same reference X values ?? I hope obtain the synchronize value Y for one reference X ex: for i:=0 to Chart1.Series[0].Count-1 do begin //retreive a X référence from fisrt serie ValRefX:= Chart1.Series[0].Xvalue ; // calcul the posi...