I have been trying to minimize a function, but I believe a syntax error is blocking the evaluation. I tried to add NumericQ to trigger the evaluation of the probability vector p, but the piecewise cost function (trivially defined here) does not evaluate to a number and I don't know why.

This code is reproducible, albite clunky as I wanted to preserve the (now useless) variables defined as closely as possible to my actual syntax.

Reproduce[v_: {{1,1},{1,2},{2,1},{2,2}},targeted_:{0.8,0.2}]:=
Module[{g,m,n,mse,piecewiseMSE, num,objective},
g = Length[First[v]];
m = Length[targeted];
n = Length[v];
mse[p__?NumericQ] :=Total[p];
piecewiseMSE[p__?NumericQ] :=Piecewise[{
 {10^9, p \[VectorLessEqual] ConstantArray[0,g]},
 {10^9, p \[VectorGreaterEqual] ConstantArray[1,g]}
 }, mse[p] ];

objective[p_?NumericQ]:= piecewiseMSE[p];
 NMinimize[objective[p],  p \[Element] Vectors[g,Reals]]

It produces an error NMinimize::nnum: The function value piecewiseMSE$92320[{0.918621,0.716689}] is not a number at {Subscript[p, 1],Subscript[p, 2]} = {0.918621,0.716689}.


1 Answer 1


Use VectorQ with the second argument NumericQ:

Reproduce[v_ : {{1, 1}, {1, 2}, {2, 1}, {2, 2}}, 
   targeted_ : {0.8, 0.2}] := 
  Module[{g, m, n, mse, piecewiseMSE, num, objective}, 
   g = Length[First[v]];
   m = Length[targeted];
   n = Length[v];
   mse[p_ /; VectorQ[p, NumericQ]] := Total[p];
   piecewiseMSE[p_ /; VectorQ[p, NumericQ]] := 
       p \[VectorLessEqual] ConstantArray[0, g]}, {10^9, 
       p \[VectorGreaterEqual] ConstantArray[1, g]}}, mse[p]];
   objective[p_ /; VectorQ[p, NumericQ]] := piecewiseMSE[p];
   NMinimize[objective[p], p \[Element] Vectors[g, Reals]]];

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.