Extract specific values of first set of matrix on base of condition from second set of matrix

There are two sets of matrix (A and B) with same size (8*8*5), A is precipitation data having random values from -10....to ....90 and B is the quality information of A with value 0, 2,10,5,1. we have to extract certain values of A which has quality (B) value only 0.

The matrix of extracted values should have same size of A and B (8*8*5)

We tried this

for i = 1:8;
for j = 1:8;
for k = 1:5;
  if B == 0
A = B; 
  end
end
end
end

and it showed the logical output with 0 and 1 but we need the actually values of A which can any from -10....to ....90. else where the values of B is not 0 should be replace with 999

Thank you in advance for help

Answer 1

[Walter Roberson]

You did not indicate what values you want in the places where B is not 0.

C = A;
C(B ~= 0) = nan;

[Shakir Hussain]

such values should be replace with 999

[Walter Roberson]

C = A;
C(B ~= 0) = 999;

[Shakir Hussain]

Thank you walter