The below line is the culprit:
elseif 3.65<k<=4.35
Specifying inequalities in matlab isn't done in the same notation as you might when writing them. If you need to find when a value is between an upper and lower bound, do something like this:
elseif 3.65 <= k && k <= 4.35
The way you have it, matlab evaluates the statement from left to right. So, if k = 6.4582, these will be the steps matlab performs:
1. (3.65 < k) <= 4.35
2. (1) <= 4.35
3. 1
Because the expression in parenthesis is true, it evaluates to "1." This leaves 1 <= 4.35, which will also return 1. But your value was 6.4582, meaning the code didn't do what you intended!
Instead, include each condition in your if statement, separating them with && symbols.
