Assuming that srcHoughMatrix is a 3-dimensional matrix :
Instead of
if (currentRadius >= MINIMUM_ALLOWED_RADIUS )
% we\'re
Matlab doesn't have the ++ operator.
However, if you would like to shorten your statement and avoid the temporary variable, you can at least write
srcHoughMatrix(index,jindex,MINIMUM_ALLOWED_RADIUS:end) = ...
srcHoughMatrix(index,jindex,MINIMUM_ALLOWED_RADIUS:end) + 1;
(assuming that currentRadius takes on all values from 1 through the 3rd-dimension-size of the array).