See the documentation for
doc transpose % .'
doc ctranspose % '
You're transposing the output of the fft() which is complex; in Matlab the ' operator is the complex transpose whereas the "dot" version .' is non-complex transpose.
So, it is doing exactly what is documented to do--
ADDENDUM
And, to emphasize what SS said, the output of fft() itself is identical as would be expected--it was given identical inputs.
The transpose operators are applied to the output of fft(); it (fft, that is) has actually nothing whatsoever to do with the result at that point; its job was done and over before the interesting action occurred.
Same as if had written
>> complex(-2,2)
ans =
-2.0000 + 2.0000i
>> complex(-2,2)'
ans =
-2.0000 - 2.0000i
>> complex(-2,2).'
ans =
-2.0000 + 2.0000i
>>
which clearly demonstrates the properties of the transpose operators has nothing to do with the source of the data (and vice versa); it simply has to be a complex value before one can observe the difference since w/o an imaginary component the complex conjugate is a "do nothing" operation.
>> [1:4]
ans =
1 2 3 4
>> [1:4]'
ans =
1
2
3
4
>> [1:4].'
ans =
1
2
3
4
>>
