How to create a grid for harmonics in plotted spectrum

I'm using a Hilbert function for a given temporel signal (acceleration,number of data points 4063) ,then i use the FFT to obtain the spectrum(250 points),my question is when i plot the spectrum how i can plot a grid or diffrent grids for a given harmonics (20 harmonics) so i can analyze the plot easily and compare it .

I'm using Matlab R2015b.

thank you.

Answer 1

[Star Strider]

I am not certain what you want.

One possibility could be to use the findpeaks (link) function to locate the peaks and locations of your Fourier transformed data, then plot the individual peaks and locations with the stem plot function. The findpeaks results would also allow you to compare the results numerically as well as graphically.

[bishop Rab]

what i mean is that i can see some vertical dashed lines that corresponds to certain values of frequencies for example:for a given frequency f0,f1....fn ,so each time i had a multiple of f0 (let's say 20n) appearing with my plotted spectrum ,i hope that you can understand me now

[Star Strider]

I believe my Answer will do what you want. The findpeaks function will return the locations (indices being the default, frequencies if you specify that) and peak values of your Fourier transformed data.

[bishop Rab]

Thank you Star Strider for your answers i appreciate your help

I found this

https://www.mathworks.com/help/signal/examples/vibration-analysis-of-rotating-machinery.html

i think that ( meshgrid ) can help also ,i'm still working on it ,it didn't work with my plot,i'm trying again.

[Star Strider]

If you want the vertical grid lines, use the 'xGrid' (link) axes property.

Example:

figure
plot(x, y)
set(gca, 'XGrid','on')