MATLAB: Counting consecutive negative numbers in an array

Question

Hello, I need to find how many times consecutive negative numbers are in the array. For example:

v = [11 2 3 -1 -2 1 -1 -1 -3 1 3 -1];

The answer must be: 3

Thank you

Answer 1

length(strfind([false v<0],[0 1]))

or

sum(diff([false v<0])==1)