In the website http://www.math.cornell.edu/~mec/Winter2009/RalucaRemus/Lecture2/lecture2.html, the author says that the matrix(adsbygoogle = window.adsbygoogle || []).push({});

B=

1 1 0 0

0 1 0 0

1 1 1 1

2 1 0 1

is not positive, yet in http://en.wikipedia.org/wiki/Nonnegative_matrix I read

"Apositive matrixis a matrix in which all the elements are greater than zero."

Discrepancy. What is going on?

Thanks.

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# Why isn't this positive?

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