Problems with snr function

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Dick Rusell
Dick Rusell on 20 Sep 2014
Commented: Image Analyst on 20 Sep 2014
I want to find the snr for signal xn and noise ns but I keep getting an error.
clear;
n = [0:1023];
omega = 0.25*pi;
xn = sin(omega*n);
count = 1024;
ns = sqrt(0.2)*randn(1,count);
r = snr(xn,ns);
plot(r);
??? Undefined function or method 'snr' for input arguments of type 'double'.

Accepted Answer

Image Analyst
Image Analyst on 20 Sep 2014
How about:
theRatio = xn ./ ns;
theSNR = mean(theRatio);
  2 Comments
Dick Rusell
Dick Rusell on 20 Sep 2014
Edited: Dick Rusell on 20 Sep 2014
I'm not sure which formula you used to find snr in the first place.
Image Analyst
Image Analyst on 20 Sep 2014
xn is your signal. ns is your noise. The SNR is theRatio xn/ns, but this gives the SNR element by element. So you have a bunch of SNR's - one for each element. So to get it down to just one SNR I took the mean of all the individual SNRs. If you want something different, then say what you want.

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More Answers (2)

Guillaume
Guillaume on 20 Sep 2014
Sounds like you don't have the signal processing toolbox.
ver
will tell you which toolboxes you have installed.
  2 Comments
Image Analyst
Image Analyst on 20 Sep 2014
Edited: Image Analyst on 20 Sep 2014
Or it's an antique version. I think snr() has not always been part of the Signal Processing Toolbox, but it's simple enough to calculate manually.
Dick Rusell
Dick Rusell on 20 Sep 2014
Edited: Dick Rusell on 20 Sep 2014
I'm using matlab 2011, how would I calculate it manually?

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Youssef  Khmou
Youssef Khmou on 20 Sep 2014
Edited: Youssef Khmou on 20 Sep 2014
Generally the formula is SNR=20log10(std(signal)/std(noise)) , in your case you have :
snr=20*log10(std(xn)/std(ns)) % 3.8dB

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