Use cvx to check a function is convex or not

I am new to cvx.I want to check a function is convex or not,like log(x) and some more complicated.
If cvx could,please tell me how,thanks very much!

Read Why isn’t CVX accepting my model? READ THIS FIRST! and CVX Users’s Guide . And if you want to get more educated about convex optimization and the theory underlying CVV’s DCP rules on convexity propagation, read

Thanks for reply.I know cvx will reject some convex function,but what i need is to use cvx to check part of convex function that follow the rules.As i understand if cvx accpet my model,then it is convex.So i want to konw how to use cvx to check a function,like log(x^2)?

This is not what CVX is for. Please, follow Mark’s instructions and read the FAQ and the documentation.