Hi Hannes,
The y-value 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 y-value, you
will need the method above to return the pen point as-well.
You can edit it so it returns a 2-array
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 x-axis and one on the graph.
The point on the x-axis may be dragged to the right and the
point on the graph follows.
How make the y-value of the point on the diagram appear?
--
GNU Dr. Geo
http://gnu.org/s/dr-geo/
http://gnu-drgeo.blogspot.com/