How to read the data from a fitted graph at specific points?

Hi

I have a graph like the attached image. How to read the data from a graph at specific points.

For example, at the values on Y-axis 0.1, 0.3, 0.5 and 0.8 then what are the corresponding values in the X-axis?

Thanks

Answer 1

[Star Strider]

I don’t know what function you used to fit your data, but I would generate the fit (or use only the data) for a range of x between about 250 and 500, and then use interp1 but with the arguments reversed from the usual:

yq = [0.1, 0.3, 0.5, 0.8];          % Y Query Points
xq = interp1(ydata, xdata, yq);     % Interpolated X Values

The reason for restricting the data to that range is due to the interp1 requirement that the data be monotonically increasing (in ‘ydata’ here), and it is not over the entire range. So you must restrict it to that range of x if you want it to work with interp1.

Answer 2

[R7 DR]

Thanks its working.

[Star Strider]

My pleasure!