Dear R Users , As a beginner in QP, I'm trying to solve a Support Vector Machine problem by a QP. In particulare I am using the quadprog package. My questions are here: 1- In the document for the package (The quadprog Package), the inequality constraint is mentioned with >= , however in a standard QP, this usaully is written with <= . This constraint should be multiplied by a negativity sign to be standard ? 2- How about nonnegativity constraints ? Are that possible to be handled via upper and lower bounds? In document, nonnegativity is not mentioned. Is there any argument for that? 3- In QP formulation we have a constant 1/2 in objective function. This should be multiplied by the user or it is done by the algorithm? 4- More important, when I multiply a b*b matrix by D in quadratic term of objective function, I get thise message: Error in solve.QP(Dmat, dvec, Amat, bvec) : matrix D in quadratic function is not positive definite! How to multiply b*b matrix by the diagonal matrix ? Thank you very much for any help. Amir --------------------------------- Park yourself in front of a world of choices in alternative vehicles. [[alternative HTML version deleted]]