Hello,

I have a similar problem to:

Suppose I plot a line from (0,0) to (1,1.5) to (2,2). Now I want to mark

(1,1.5) with a green circle. How is that done?

I am performing a curve fit and also showing a distribution in my plot.

In order to help the reader to evaluate the result I would like to draw certain

boundaries (vertical and horizontal line).

While I am aware on how to draw such lines, I would like to know wheather there

are some functions in matplotlib which help me to retrieve the coordinates

a) at which two curves intersect

b) at which a distribution reaches a certain value?

Example:

How do I get the y-axis value which is reached by the green curve in

http://matplotlib.sourceforge.net/_images/histogram_demo_extended_021.png

a x-axis value of in 175?

I could proably use a solver from numpy like

http://docs.scipy.org/doc/numpy/reference/generated/numpy.linalg.solve.html#numpy.linalg.solve

but if I plot a distribution, the equation of the envelove is unknown at the

first place.

I'd appreciate your help or pointers to examples.

Thanks a lot in advance,

Timmie