How to replace values less than equal to zero values in a matrix?

I have a marix of 44450*8 dimention, which contain some zero and negative values, I want to replace them with NaN. how to do that?

Answer 1

[Adam]

myMatrix( myMatrix <= 0 ) = NaN

[Puspa patra]

Thank you

Answer 2

[Sai Naga Raju]

matrix (matrix<=0)= NaN

[laith awwad]

HOW TO NAME THE VARIABLE BECAUSE IF I WRIGHT IT GIVES ME AN ERROR FOR EXAMPLE e =matrix (matrix<=0)= NaN;