You can use the regular "plot" function inside a Simulink model by calling it inside a MATLAB Function block.
... with one caveat. You have to declare it as extrinsic so that MATLAB calls the function using the interpreter instead of by trying to compile it. Therefore, this will only plot if you're running the simulation on your computer (and not if you plan on generating code from the model).
The documentation has this example right here (just replace the "patch" function with "plot"): http://www.mathworks.com/help/simulink/ug/calling-matlab-functions.html#bru21fv
- Sebastian
