Function, How to write this formula in Matlab

I have been trying to write this formula in matlab, but I have not had many results. The formula is as follows:

in addition, the Ln must have a conditional, where, if Pi is negative or equal to 0, the result of the ln of that Pi is 0.

If someone can help me, it would be very helpful

Thanks

Answer 1

[Walter Roberson]

W = log(p);
W(p <= 0) = 0;
N = exp(-sum( p .* W));

[Santiago]

Hi Walter, thank you for your answer.

But I made some mistakes when i tried to explain my question

[Walter Roberson]

Ln = log(p);
Ln(p <= 0) = 0;
N = exp(-sum( p .* Ln));