In keeping with a question about the fuzzy toolbox, my response is an oldie, but moldy. That is, do you actually have that toolbox? Remember that many tools are not part of MATLAB proper, but require you have a specific toolbox. On Answers, we can see pretty much everything. (Ok, mostly.)
which fuzzy
But if you do not have a fuzzy toolbox license, you don't have that toolbox. (You can then get it, of course.) So at the command line, ask MATLAB what it thinks. Type the command ver. It will tell you what it thinks you have.
ver
