Show FFT plot of matrix

[mimi99]

Hello everybody,

I would make a programm to show the FFT of matlab matrix, I try to do it but I remark that the spectrum is not correct (It's not the frequency plot).

This is the programm, can you help me please I need it so much

Thank you so much

[mimi99]

Help pllz

[altenbach]

Attach your VI and some typical data. We cannot see what's​ going if there are express VIs and dynamic data. Why do you think the graph is wrong? Did you correctly configure f0 and DF? How about renaming the x axis?

[altenbach]

Attach your VI and some typical data. We cannot see what's​ going if there are express VIs and dynamic data. Why do you think the graph is wrong? Did you correctly configure f0 and DF? How about renaming the x axis?

What's in these subvis? Attach them too!

[mimi99]

Hello everyone,

I am trying to make the Spectrum analysis from a Matlab Matrix. The matrix has this form: 50 x 23800 (the rows are amplitude, the columns are the time). For example, for 1s, this is 23800 samples.

[RavensFan]

Asmae,

You didn't follow Altenbach's request.  He asked for the VI with some typical data saved within it.  Instead you attached the same images you attached before, none of which are a VI.

[mimi99]

okey, this is the VI. Data has .mat as extension, it would'nt be loaded here:

[mimi99]

I do the same thing on Matlab, I get this spectrum. It's correct

I don't know how to implement this on Labview, it's not work. But, Is it possible to indicate the sample frequency on Labview? because I don't do this in my programm, How do I do???

[Chase.E]

This is a great White Paper explaining the functionality of FFTs in LabVIEW. 

http://www.ni.com/white-paper/4541/en/

What kind of FFT are we taking? Double sided, single sided? Since we seem to be passing in discrete data, what do you mean by controlling the sampling?

My advice would be to use context help on the FFT function you are using, it seems the data going in may be in a different format that what it is expecting. It might also benefit you to manipulate your input data into an array before passing it into the FFT function. Different versions have different functions behave differently, so which version of LabVIEW are we working in?

[mimi99]

Hello,

I use Labview 2015, I would use FFT single sided. I mean by controling sampling: the frequency to use to sample the signal. I try to use array before calculating FFT, but it doesn't work.

And when I change FFT by spectral measurement, the waveform gives just 1 peak. I think this peak is the result of the first vector from my data's matrice.

I give you the new programm, the result of spectral measurement and a figure of my data on Matlab.

I need your help, thank you