A = [0 0 0 2095 2030
0 2030 2030 2030 2030
0 0 2095 2055 2065
2065 2055 2050 2030 2030]
targetval = 2030;
n_rows = size(A,1);
B = zeros(1,n_rows); % pre-allocate vector B with a zero for each row of A.
for i = 1:n_rows
d = A(i,:);
idx = find(d==targetval, 1, 'first'); % find the first occurrence of targetval in row i.
if ~isempty(idx) % if there is one, store it as element i of B;
B(i) = idx; % (otherwise element i of B remains 0).
end
end
disp(B);
