Madeleine Udell

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This paper describes Convex, a convex optimization modeling framework in Julia. Convex translates problems from a user-friendly functional language into an abstract syntax tree describing the problem. This concise representation of the global structure of the problem allows Convex to infer whether the problem complies with the rules of disciplined convex(More)
Principal components analysis (PCA) is a well-known technique for approximating a data set represented by a matrix by a low rank matrix. Here, we extend the idea of PCA to handle arbitrary data sets consisting of numerical, Boolean, categorical, ordinal, and other data types. This framework encompasses many well known techniques in data analysis, such as(More)
We present two modifications of the flux balance analysis (FBA) metabolic modeling framework which relax implicit assumptions of the biomass reaction. Our flexible flux balance analysis (flexFBA) objective removes the fixed proportion between reactants, and can therefore produce a subset of biomass reactants. Our time-linked flux balance analysis (tFBA)(More)
We consider the problem of minimizing a sum of non-convex functions over a compact domain, subject to linear inequality and equality constraints. Approximate solutions can be found by solving a convex-ified version of the problem, in which each function in the objective is replaced by its convex envelope. We propose a randomized algorithm to solve the(More)
This paper develops a suite of algorithms for constructing low-rank approximations of an input matrix from a random linear image of the matrix, called a sketch. These methods can preserve structural properties of the input matrix, such as positive-semidefiniteness, and they can produce approximations with a user-specified rank. The algorithms are simple,(More)
We consider the problem of learning the preferences of a heterogeneous population by observing choices from an assortment of products, ads, or other offerings. Our observation model takes a form common in assortment planning applications: each arriving customer is offered an assortment consisting of a subset of all possible offerings; we observe only the(More)
We consider the problem of learning the preferences of a heterogeneous customer population by observing their choices from an assortment of products, ads, or other offerings. Our observation model takes a form common in assortment planning: each arriving customer chooses from an assortment of offerings consisting of a subset of all possibilities.(More)
—Broadband internet service providers (ISPs) are for-profit companies: they provide high speed internet service to customers in order to maximize revenue. Their revenue depends on prices they are able to charge the customers, which in turn depends on the data rates provided. This paper defines the revenue capacity of a communication channel as the maximum(More)
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