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coherence plot and correlation plot,time domain to frequency domain

Asked by Sana Ejaz on 1 Jul 2019
Latest activity Answered by Navya Seelam on 17 Jul 2019
Hi ,
I have attached a sample data.I want to create a correlation as well as coherence plot for the attached time series data.
In order to understand the difference between time and frequency domain of time series I need to plot both correlation and coherence of same time series so that I can spot and understand the difference.Since I am new to the frequency domain concept I don't know how to measure coherence and how to make coherence plot.My understanding is that in order to measure coherence I would need to convert the time series that is in time domain to frequency domain.But I dont know how to do that.
Would highly appreciate if someone can help.

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1 Answer

Answer by Navya Seelam on 17 Jul 2019
 Accepted Answer

Hi,
If you have the Signal Processing Toolbox, use the function "mscohere" to plot coherence.
n = 0:599;
x = cos(pi/4*n)+randn(size(n));
y = 1/2*sin(pi/4*n)+randn(size(n));
[Cxy,W] = mscohere(x,y);
Plot(W,Cxy)
You can obtain the correlation using the function "xcorr"
C=xcorr(x,y);
For more details check the MATLAB documentation of the above functions

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