MATLAB: How to plus two nan matrix

Question

If my two matrix are

a=3*3,b=3*3,c=3*3

a=[1 2 3,4 5 nan,7 nan 9]

b=[nan 3 3,4 5 6,nan 8 9]

c=a+b

Is that possible that c=[1 5 6,8 10 6,7 8 18]

How to calculate?

Thanks

Answer 1

c = a + b;
c(isnan(c)) = a(isnan(c));
c(isnan(c)) = b(isnan(c));