converting atan2 output to 360 deg

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Hi, I'm using the function atan2, however my output is from -180 to 180 degrees (I converted from radians) How do I modify it such that it outputs a value from 0-360 degrees?
winddir = (atan2(Vi,Ui))*(180/pi);
  1 Commento
Image Analyst
Image Analyst il 13 Apr 2015
There is an atan2d() function you know. All the functions have "d" versions that work in degrees instead of radians. Though it goes from -180 to +180.

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John D'Errico
John D'Errico il 14 Apr 2015
Modificato: John D'Errico il 14 Apr 2015
Since it will be periodic, just add 360 if the value is less than 0. This will suffice to correct the negative angles.
winddir = winddir + (winddir < 0)*360;
You can use atan2d if you prefer to work in degrees, but it will map to the same range, [-180,180], so you will still need to correct for the negative angles.
If you wanted a simple expression that works in one line of code, this should do:
winddir = atan2d(Vi,Ui) + 360*(Vi<0);

Più risposte (2)

Stephen23
Stephen23 il 30 Mag 2022
Modificato: Stephen23 il 30 Mag 2022
The simple, robust, and efficient solution is to use MOD:
mod(atan2d(Y,X),360)

theodore panagos
theodore panagos il 7 Nov 2018
You can use the formula:
atan(x,y)=180/pi()*(pi()-p()/2*(1+sign(x))*(1-sign(y^2))-pi()/4*(2+sign(x))*sign(y)
-sign(x*y)*atan((abs(x)-abs(y))/(abs(x)+abs(y))))
That formula give the angle from 0 to 360 degrees for any value of x and y.
x=x2-x1 and y=y2-y1
For x=y=0 the result is undefined.
  2 Commenti
theodore panagos
theodore panagos il 7 Nov 2018
In the formula put pi()/2 instead p()/2
Nicolas soto vallejos
Nicolas soto vallejos il 30 Mag 2022
Have to say this formula is awsome if you only need to know what quarternal direction the vector is traveling in you could just use the first part. sure only returns in 45 deg but it makes it easier to work with and ofcourse you could allways use the entire thing if you need exact angles but i'm amazed at the brillians of this formula 10/10!

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