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Frequency spectrum - Reading certain y-values

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Mepe
Mepe on 27 Mar 2019
Edited: Adam Danz on 27 Mar 2019
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!
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Mepe
Mepe on 27 Mar 2019
As already described, I would like to read defined x-values with the corresponding y-values. Attached are my measurement.
untitled.jpg
Thanks!

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Accepted Answer

Adam Danz
Adam Danz on 27 Mar 2019
Edited: Adam Danz on 27 Mar 2019
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.

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