attached are matlab compatible implementations of the functions sumsqr, sumabs, meansqr, and meanabs.  they are all fairly similar in behavior and were introduced in matlab <2010.  After some input handling, they all just call elementwise sqr or abs followed by sum or mean over all elements to return a scalar, skipping over anything failing an isfinite() test.

I noticed there are sumsq and meansq functions that were probably introduced a long time ago that are not compatible with the matlab sumsqr and meansqr functions. their behavior is different enough it's probably worth keeping the separate functions rather than just modifying the octave functions, since the names don't match anyway. (similar to what was done with repelem and repelems).

Of note these functions can handle numeric, char, and logical inputs, as well as arbitrarily shaped cell arrays of the same. 

I did verify that these functions work with complex inputs, whereas the matlab functions error for any complex valued inputs, and Octave's meansq & sumsq functions produce odd results with complex values. (meansq appears to ignore complex numbers, sumsq appears to apply sum((abs(Z))^2) )

will generate and a patch once i have a number.