How to modify a variable inside of a loop and use it outside the loop

I'm writing an algorithm right now, and I'm having trouble with my variables. For instance, the variable values modified inside of a loop are not being saved when I exit that loop. How do I get the correct number set as that variable? For example, in this loop the est_trains_per_hr is still acting as 0 after the loop

est_trains_per_hr = 0 ;
for time_num = 1 : length(times)
	time = times(time_num) ;
	if time >= 800 && time < 900
		est_trains_per_hr = est_trains_per_hr + 1 ;
	end
end 

Answer 1

[James Tursa]

What does this show:

sum(times(:)>=800 & times(:)<900)