I think the easiest way to do this is to use the imcalc function in SPM.

Thanks Xin Di!

Can you elaborate on that, please!

In ImCalc, you can specify the r map as input images. If you put the equation of FIsher's z transformation as expression, it can give you the z map. The expression may like this: 0.5*log((1+i1)./(1-i1)). Please see attached Figure also.

Try this code on Matlab :

function[z]=fisherz(r)

%FISHERZ Fisher's Z-transform.

% Z = FISHERZ(R) returns the Fisher's Z-transform of the correlation

% coefficient R.

r=r(:);

z=.5.*log((1+r)./(1-r));