function rlev = rain_level(rainfall)
rlev = ones(size(rainfall));
idx = rainfall > 0.5 & rainfall < 1.1;
rlev(idx) = 2;
idx = rainfall >= 1.1 | rainfall == 0.5;
rlev(idx) = 3;
end
The "rainfall == 0.5" is necessary because 0.5 exactly is not less than 0.5 and is not between 0.5 and 1.1 either; you indicated 3 "otherwise" so the 3 has to apply to all ranges not listed, including the 0.5 exactly.
1.1 exactly cannot happen in binary floating point (1/10th is an infinite repeating number in binary) so the question of whether 1.1 exactly belongs in level 2 or 3 becomes irrelevant, and we might as well code >= on the 1.1 for clarity.
