Separate inhale and exhale duration

Hello all,

using NI myRIO I obtained an array of intersection points between a signal and a threshold, every two values represent the rise and fall of an inhale and exhale, repectively.

I want to subtract each two values and store them in new arrays, inhale time, exhale time and breath time.

Now i know there's a problem in the loops I made but i don't know how to fix them, please help me. I'm getting the same values of duration, maybe the j is not updating

the attached picture is the signal where the values were obtained from.

breath=[903, 1979, 2313, 3550, 3870, 4947, 5232, 6517, 6867, 7818, 8181, 9512];
count=length(breath)/2 ;       %count peaks (inhales and exhales)

%Find duration of inhale & exhale
INduration=zeros(1,count/2);
for k=1:count/2      %durations of inhale
    for j=1:4:length(breath)-4
    INduration(k)= breath(j+1)-breath(j);
    end
end
EXduration=zeros(1,count/2);
for n=1:count/2      %durations of exhale
    for j=3:4:length(breath)-4
    EXduration(n)= breath(j+1)-breath(j);
    end
end
BRduration=zeros(1,count/2);
for r=1:count/2      %durations of whole breath
    for j=1:4:length(breath)-4
    BRduration(r)= breath(j+3)-breath(j);
    end
end

[Image Analyst]

Set a breakpoint on the lines inside the for j loop, and see if the program stops there and if indeed j is changing? I think you'll see it does change

[Majd AG]

Thank you for answering, I tried displaying the j inside the first loop and it alternates between two values 1&5 three times, what does that mean?

Answer 1

[Peter Perkins]

You don't need any loops.

Your picture doesn't seem to match your description, but if each sret of four values corresponds to inhale start, inhale stop, exhale start, exhale stop, then do this:

>> breath = seconds([903, 1979, 2313, 3550, 3870, 4947, 5232, 6517, 6867, 7818, 8181, 9512])
breath = 
  1×12 duration array
    903 sec   1979 sec   2313 sec   3550 sec   3870 sec   4947 sec   5232 sec   6517 sec   6867 sec   7818 sec   8181 sec   9512 sec
>> inhale = reshape(breath([1 2 5 6 9 10]),[2 3])
inhale = 
  2×3 duration array
    903 sec   3870 sec   6867 sec
   1979 sec   4947 sec   7818 sec
>> inhaleDuration = diff(inhale)
inhaleDuration = 
  1×3 duration array
   1076 sec   1077 sec    951 sec
   

and similarly for the others.