How to determine if angles match

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I am trying to write code to determine when two precession angles match. Matlab keeps skipping to the last else statement regardless of which elseif statement should be taking precedence.
prec1 = rad2deg(acos(C21./sin(deg2rad(nutation))));
Unrecognized function or variable 'C21'.
prec2 = rad2deg(asin(C31./sin(deg2rad(nutation))));
if abs(prec1 - prec2) < 10^-3
prec = prec1;
elseif abs(prec1 - (180 - prec2))< 10^-3
prec = prec1;
elseif abs((360 - prec1) - prec2) < 10^-3
prec = prec2;
else
prec = 360 - prec1;
end
  4 Comments
Madeleine
Madeleine on 20 Feb 2024
C21, C23, and nutation are arrays that contain ten values calculated earlier in the code.
C12 and C23 are elements of a direction cosine matrix for a two body 1-3-1 rotation sequence and nutation is the angle about body fixed axis u1. precession is the angle about body fixed axis u3.
Madeleine
Madeleine on 20 Feb 2024
C12 =
0
0.5207
-0.2255
0.6599
0.0813
0.4857
-0.0558
-0.3070
-0.2298
-0.7950
C23 =
0
0.4887
0.0624
-0.3257
0.0516
-0.7995
0.3638
-0.7010
0.2401
-0.6821
nutation =
0
116.6697
53.6137
79.6703
102.4619
32.9411
127.0446
18.0036
103.4862
69.9394

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Accepted Answer

Walter Roberson
Walter Roberson on 20 Feb 2024
You would get that behavior if prec1 or prec2 are non-scalar and it does not happen that all of the values pass the tests.
  1 Comment
Madeleine
Madeleine on 21 Feb 2024
How do i make my variables scalar. I tried using ANY and ALL functions but it I still get a non-scalar error

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