It's some time I was thinking about solving this problem. I have a registration of angular data (Angle(~20000,1)) variating between 0 and 355 (a potentiometer attached to a rotary testing machine), and I wanted to convert it in an incremental form, since I want the final total angular displacement. The main issue is that between 355 and the next 0 there are no jumps but a fast decrement (with strongly negative slope in time vs angle space). I've tried 2 ways up to now:
Calculate the Angslope=diff(Angle), extract with find the indexes j1=find(Angslope>0.2 & Angslope<0.2) to avoid the negative slopes due to the inversion of angular signal, then try to apply those indexes to the original Angle(n,1), as Angle2=Angle(j1). The trouble is the n-1 length of Angslope and the fact that somehow there is not a simple shift of my indexes of one position.
For cycles and logical, wanting to exclude data if the previous one is < the current value,etc
Angle2=zeros(size(Angle,1),1);
for i=2:size(Angle,1)
if Angle(i,1)<Angle(i-1,1)
Angle2(i,1)=NaN;
else Angle2(i,1)=Angle(i,1);
end
end
Which works good, but I don't know how to "match up" the single increment steps I obtain!
Any help or simple comment would be of great help!!
You are probably looking for the unwrap function. For this you have to convert your angles into radians, but that's not a big deal.
You can get the increments in one line:
Inc = diff(unwrap(Angle*pi/180))*180/pi;
and your total angular displacement:
Tot = sum(Inc);
Best,