How to make NaN data

Hello,

here is the data.

a = [-2 -1 2 3]
b = [1 2 3 4]
c=a.*b
c = [-2 -2 6 12] 

right?

but I want to make the NaN value to the negative c data..

in this case, c = [NaN NaN 6 12]

How to do that?

values of b can vary depending on my initial condition, so I need the code which change to NaN automatically.

Answer 1

[madhan ravi]

c(c<0) = NaN

[hj lee]

Thank you very much!!!