Re: Octave 4.0.3: normxcorr2 producing unexpected result

[Hartmut]

When you use t = [1 1 1] you will get only 0s as result. And this is also
correct.

Reason:The normalized cross correlation is also normalized to the standard
deviation of s and t. So in places where s or t have a standard deviation of
0 (like t in your case, try std(t) ) you will get an undefined result.
Matlab decided to return a 0 value is this case. For the definition of the
normalized cross correlation as well as for this Matlab behavior, see [1].

If you want so search for image templates that are fully flat (i.e. with a
standard deviation zero) than you should probably be using something
different, but not normxcorr2. You might want to try corrcoef (in future
Octave version 4.4) for your 1-D example, your just use stdfilt or rangefilt
on real 2D images.

     Hartmut


[1] Matlab help page of normxcorr2: 
     Defintion:
https://de.mathworks.com/help/images/ref/normxcorr2.html#bvibmz_-5
     Dealing with std=0:
https://de.mathworks.com/help/images/ref/normxcorr2.html#bvh5vek-3



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