Check if any element of Eigen::Matrix is different from zero

Question

I have an Eigen::Matrix<double, Dynamic, Dynamic>, and I need to check if any of its elements is different from 0.

I tried the following code:

Matrix<double, Dynamic, Dynamic> m;
bool f = (m != 0.0).any();

But I got a compiler error.

Invalid operands to binary expression ('const Eigen::Matrix' and 'double')

not related to the error, but you should compare floating points to zero via `(abs(m) < eps)` — 463035818_is_not_an_ai, Dec 02 '15 at 15:38

score 11 · Accepted Answer · answered Dec 02 '15 at 16:19

11

In Eigen, most of the element-wise operations are handled by an Array class. Fortunately, there is a simple way to use them on Matrix objects. Try

bool f = (m.array() != 0.0).any();

answered Dec 02 '15 at 16:19

Avi Ginsburg

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Does the array() method create a new object? I am concerned about performance. – Nick Dec 02 '15 at 21:05
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Nope. It just treats the existing object as an Array. – Avi Ginsburg Dec 03 '15 at 04:05

score 2 · Answer 2 · answered Jun 04 '21 at 06:36

2

Another option is

bool f = !m.isZero();

It should work for both Array and Matrix

answered Jun 04 '21 at 06:36

ThomasHH

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Check if any element of Eigen::Matrix is different from zero

2 Answers2