Hi Hannes,
The yvalue does not exist. It is not needed to
plot the curve. Indeed, the plot is based on the geometric
locus, it depends on a mobile point on a line and dependent
point, here a point whose coordinates are computed by the block
of code.
See its implementation in the ckass DrGeoSketch.
It is a kind of user side implementation, not part of the core
Dr. Geo model:
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plot: f from: x0 to: x1
 mobile s pen
s := self segment: x0@0 to: x1@0.
mobile := self pointOnLine: s at: 0.
pen := self
point: [:item  item point x @ (f value: item point x)]
parent: mobile.
^ (self locusOf: pen when: mobile) color: Color blue

To compute by yourself the yvalue, you
will need the method above to return the pen point aswell.
You can edit it so it returns a 2array
with both the locus and the pen.
Hilaire
Le 28/12/2023 à 13:09, H. Hirzel a
écrit :
Hi Hilaire
I have the following code
 sketch f 
sketch := DrGeoSketch new axesOn gridOn.
f := [ :x  0.2 * x * x  1].
sketch plot: f from: 6 to: 6.
If I execute it I get two points without names.
One on the xaxis and one on the graph.
The point on the xaxis may be dragged to the right and the
point on the graph follows.
How make the yvalue of the point on the diagram appear?

GNU Dr. Geo
http://gnu.org/s/drgeo/
http://gnudrgeo.blogspot.com/