Hi, I’m wondering if there is a way to express log(x/(1-x)) for 0<x<1 in cvx. Thanks a lot

That is concave for 0 <= x <= 1/2, and convex for x>= 1/2.

Please carefully (re)read the link you were previously provided.

My bad. Actually, my constraint is like 1/(1+exp(-x))>=y, which I believe to be convex. Is there a way to express it in cvx? Thanks

The LHS is convex for x <= 0, and concave for x>= 0. The LHS needs to be concave in order for the constraint to be convex. Given that the LHS switches convexity over its natural domain, I am not optimistic for there being a way to express that in CVX, even if x is constrained to be >= 0.