# Covex Optimization techniques for Approximating convex sets

 0 Consider a convex set $$C$$. I want to approximate this set by some parametric inequalities of the form $$f_i \le 0 ~\forall i=1, ..., M$$. Here $$f_i$$ are parametrized by some parameters (e.g. could be hyperplanes etc..). I want to know if I can compute these $$f_i \forall i$$ by some convex optimization. I am aware of outer approximation techniques for convex sets. However they are iterative in nature. I want to perform this step as a convex optimization. For example, I can say that I approximate the convex set by a linear inequality and I then run an optimization to compute the parameters of the linear inequality (while optimizing some metric). asked 19 Jun '15, 20:05 anon123 33●1●6 accept rate: 0% How is $$C$$ defined/specified? Is it the solution set of a system of explicit inequalities? (20 Jun '15, 16:23) Paul Rubin ♦♦ Let us assume for the time being that C is characterized by some nonlinear inequalities which I know. Can I do something then? I can outer approximate each of these inequalities by taking derivatives. E.g if there are M inequalities I can then select M points and construct an outer approximation around those points. I want to know how to select these M points so that I arrive at the best possible approximation. (23 Jun '15, 18:21) anon123 possibly more than M points too. But my goal is to cleverly select these points. (23 Jun '15, 18:22) anon123 If the convex set is already characterized by known nonlinear inequalities, let's say c_i <= 0, then what's "wrong" or undesirable about them? You have to tell us what you don't like about the existing characterization (c_i <= 0) in order for us to tell you a "better" approximation. Your existing characterization is presumably sharp, so you seems to want to give up some sharpness in exchange for functions f_i which you "like" better than c_i. But you haven't told us what kind of functions f_i you like better than c_i. (23 Jun '15, 19:20) Mark L Stone
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