ya 13 13 SolutionThat function was introduced in release R20

Solution

That function was introduced in release R2016b of Symbolic Math Toolbox. Looking at the \"Functionality being removed or changed\" table, in earlier releases you can use \"ezplot\".

Note, however, that the syntax of those two functions may be different and ezplot may not have all the functionality of fimplicit.

I can help you with the code if you can post .m file here.