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Calculating the distance between two matrices Matlab

Asked by alladin on 2 Dec 2014
Latest activity Commented on by alladin on 2 Dec 2014
I want to calculate the distance between two different DFT results after i performed this code:
I1 = imread('sample1');%read the images
I2 = imread('sample2');
GI1 = rgb2gray(I1) %change it to grayscale
GI2 = rgb2gray(I2)
DftR1 = DFT(GI1) %perform the 2-dimensional DFT(a function that i built it myself)
DftR2 = DFT(GI2)
so far it all worked; however when i want to compare the results of the DFT using this code:
Distance = pdist2(DftR1, DftR2)
I get this particular error: Error using pdist2 (line 224) PDIST2 does not accept complex data for built-in distances.

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2 Answers

Answer by Star Strider
on 2 Dec 2014
 Accepted Answer

The DFT that the code you posted previously returns will be complex.
If pdist2 wants only real values,
Distance = pdist2(abs(DftR1), abs(DftR2));
will likely work.

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Thank you, it worked, but the issue that the result was a matrix, i thought by calculating the distance i will get only one value so that i can tell whether the results match or not.
If you have an idea on how to do it please let me know. I appreciate your help
My pleasure.
The pdist2 function returns a matrix by definition. You can force the matrix to become only value by creating a vector out of it and then performing the operation you believe best suits your application. The mean or standard deviation might be most appropriate:
Dmean = mean(Distance(:));
Dstdv = std(Distance(:));
I appreciate your help thank you

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Answer by Deepesh B on 2 Dec 2014

Hi U have to use
abs
before applying
pdist2
because after fft it will have complex numbers

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