Is the Matrix B Positive or Not?

[nomadreid]

In the website http://www.math.cornell.edu/~mec/Winter2009/RalucaRemus/Lecture2/lecture2.html, the author says that the matrix
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
"A positive matrix is a matrix in which all the elements are greater than zero."
Discrepancy. What is going on?
Thanks.

 

[Stephen Tashi]

I haven't read the links, but zero is not greater than zero. So why would a matrix containing a zero be "positive"?

 

[Mark44]

From the wiki page,

A nonnegative matrix is a matrix in which all the elements are equal to or greater than zero.

A positive matrix is a matrix in which all the elements are greater than zero.

Nonnegative isn't the same thing as positive.

 

[nomadreid]

Oops. Thanks, Stephen Tashi and Mark44. I should get more sleep...