I have this test implemented in my code, when I import a numeric matrix, which I thought would be bulletproof, but it's failing in this case:

In[]:= MatrixQ[{{}, {}}, NumericQ[#] && MatchQ[#, _Real] &]

Out[]= True

I don't get it.


1 Answer 1


Because there are no elements in your matrix. So there is no element which is not numeric and real.

MatrixQ[{{}, {}}, False &]

returns True too.

So you have to exclude that case:

MatrixQ[##, NumericQ[#] && MatchQ[#, _Real] &] && !MatrixQ[##, False &] &
  • 1
    $\begingroup$ I'd find the example MatrixQ[{{}, {}}, False &] somewhat more convincing. (Typo? If not, consider MatrixQ[{{1}, {1}}, True].) Or maybe MatrixQ[{{}, {}}, Print] vs. MatrixQ[{{1}, {1}}, Print]. In any case, +1. $\endgroup$
    – Michael E2
    Oct 15, 2016 at 21:40
  • $\begingroup$ @MichaelE2 Whoops. Thanks for pointing out $\endgroup$
    – meneken17
    Oct 15, 2016 at 21:43
  • $\begingroup$ Thanks! And how can I catch this case? I have tried several things without success. $\endgroup$
    – Santiago
    Oct 16, 2016 at 9:18

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