Single Plot with Two Y-Axes

Hello everyone.

My Objective: To plot a single graph of a dataset that contains values of Index (x) vs. Frequency (y) values, where Index is a vector and Frequency is a matrix containing different curves. That part has been accomplished. However, I would now like to add the corresponding Wavelength values on the right hand side of the plot. That is where I am having difficulties.

Attempted Solutions I attempted to use plotyy to possibly plot another graph of Index vs. Wavelength and then hiding the plot by coloring it white. However, I was not able to acquire the desired result since the scales of Wavelength did not depict corresponding Frequency values.

If, perhaps, there is another possible way of depicting Wavelength values with their corresponding Frequency values, I would be happy to implement that instead of labeling the y-axis on the right.

Thank you.