"Why there is no space after the equal sign?"
It has nothing to do with fprintf. As the strcat clearly states, strcat removes whitespace characters from the end of char vectors: "For character array inputs, strcat removes trailing ASCII white-space characters". If you want to keep the space characters, put it into a scalar cell array, like this:
{' = '}
But really you would be much better off just writing a proper format string for fprintf, rather than using both strcat and fprintf.
