Getting matlab to read values of a graph

How do I read the values of voltage when current is zero, and current when voltage is zero from a current voltage graph in matlab

[the cyclist]

Do you only have the image file (e.g. a *.png file), or do you have the actual MATLAB figure handy and you are trying to get the data from there?

[Tara Milne]

I have the actual Matlab figure, I made the current column one vector and voltage the other and did plot(current, voltage)

[Tara Milne]

btw I don't have data points for when the current and voltage are zero, but the graph goes through these points

Answer 1

[Walter Roberson]

First step:

v_at_c0 = interp1(current, voltage, 0);   %estimate of voltage at which current is 0

For finding the current at which the voltage becomes 0, a sample graph would help. In some cases it is very easy, in other cases it takes a bunch more work.