Replace zeros with a number

I am trying to create an upper bound condition for a portfolio weighting problem to equal 2%. How can I replace the zeros in the following matrix to equal 0.02?

UB = zeros(N,1)

Thanks

Answer 1

[madhan ravi]

UB(UB==0) = 0.02;
% why not 
UB = 0.02*ones(N,1) % in the first place?