Efficient way to count the number of times a value changes to a particular value in an array

What is the best way to do the following:

count=0;  
for i=2:length(x)
  if x(i)==1 && x(i-1)~=1
     count=count+1;
  end
end

Answer 1

[the cyclist]

sum(x(2:end)==1 & x(1:end-1)~=1)