Re: Projection on the axis X.

[Przemek Klosowski]

On 5/22/19 7:53 AM, FH_2137 wrote:

It is possible to projection points from plot to X axis? Probably this is
popular topic, but i do not found nothing in internet.

Please explain what exactly do you want to accomplish. From your picture, it looks like you have a plot of several data points, linked by straight lines, and a horizontal construction line (presumably placed by mouse movements) intersecting those plot lines. It looks like you want to draw vertical lines from those intersections down to the X axis.

I don't know of an existing functionality in Octave graphics system that does that, but you can of course synthesize it from existing primitives:

- find Y position of the mouse:  [x,y,button]=ginput(1)

- draw a horizontal line at that Y position: line([0 1],[Y Y])

- find intersections with an interpolation of your data points:

      https://math.stackexchange.com/questions/942166/finding-where-plots-may-cross-with-octave-matlab

- draw vertical lines from the intersection points: line([X X],[0 1])