How to compare an integer to the elements of a vector?

So I have a single value u ( between 0 and one generated by rand) and I have a n dimensional vector, let's say C .I want to compare this u to every element of the C vector and find the lowest i such that u < C(i), for example u = 0.2 and C = [0.1 0.15 0.21 0.37 0.54 0.87 1].' , then my algorithms needs to find 0.21 which is C(3) and gives me the i (=3 in this case) back.

Answer 1

[Star Strider]

Another approach:

val = min(C(u<C));
idx = find(C == val);

.

Answer 2

[KSSV]

idx = find(u<C) ;
idx(1)

Read about find, you should have an option of getting first index striaght away.