Use ‘logical indexing’:
M = randi(10,6)
Mnew = M+(M<5)*10
producing (in this random instance):
M =
8 6 5 2 1 2
9 4 10 6 3 1
2 2 2 3 1 4
2 3 8 2 5 5
4 10 8 3 1 2
1 7 6 9 9 10
Mnew =
8 6 5 12 11 12
9 14 10 6 13 11
12 12 12 13 11 14
12 13 8 12 5 5
14 10 8 13 11 12
11 7 6 9 9 10
