Frequency spectrum - Reading certain y-values

Given is the frequency spectrum of a measurement. The x-axis represents the frequency, the y-axis the amplitude. These are stored as individual column vectors. I am now interested in the amplitude values at certain frequencies (e.g., 2,3,4,5 MHz). How can I best "read" these and store them in a separate vector / matrix?

Thanks a lot!

[Adam Danz]

If you share a sample of your data it would be easier to visualize what's going on.

[Mepe]

As already described, I would like to read defined x-values with the corresponding y-values. Attached are my measurement.

Thanks!

Answer 1

[Adam Danz]

How can I best "read" these and store them in a separate vector / matrix?

file = 'C:\Users\name\Documents\MATLAB\5M_60°_4_5MHz_20V_C.csv'; 
num = xlsread(file); 

>> size(num)
%ans =
%       16385           2

I am now interested in the amplitude values at certain frequencies (e.g., 2,3,4,5 MHz).

%find freq closest to target
target = 2.0;
[~, closestIdx] = min(abs(num(:,1) - target));
num(closestIdx,:)
%ans =
%       1.9995      -74.481

If you're looking for specific peaks, check out findpeaks() function.