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Re: Calculate angle on 0-360 scale from positive and negatives x and y vectors.
Posted:
Mar 20, 2011 7:27 PM
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"Thomas " <wandernmann@gmail.com> writes:
>> If you want it to range between 0 and 2*pi, just do this:
>>
>> a = mod(atan2(y,x),2*pi);
>>
>> Roger Stafford
> Ahh...atan2 and mod were just the functions I was looking for,
You should not use 'mod' in combination with multiples of pi because
it may result in ulp errors.
a = atan2(y, x);
tem = (a < 0);
a(tem) = a(tem) + 2 .* pi;
is the accurate form.
>> x = (-2*pi:pi/3:2*pi)';
>> [x, sin(x) == sin(mod(x, 2*pi))]
ans =
-6.2832 0
-5.236 0
-4.1888 0
-3.1416 0
-2.0944 0
-1.0472 0
0 1
1.0472 1
2.0944 1
3.1416 1
4.1888 1
5.236 1
6.2832 0
--
Ralph Schleicher <http://ralph-schleicher.de>
Development * Consulting * Training
Mathematical Modeling and Simulation
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