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

read data from a fitted graph

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

Best Answer

  • 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.