cf.Data.arctan2

classmethod Data.arctan2(x1, x2)

Element-wise arc tangent of x1/x2 with correct quadrant.

The quadrant (i.e. branch) is chosen so that arctan2(y, x) is the signed angle in radians between the ray ending at the origin and passing through the point (1, 0), and the ray ending at the origin and passing through the point (x, y). (Note the role reversal: the “y-coordinate” is the first function parameter, the “x-coordinate” is the second.) By IEEE convention, this function is defined for x = +/-0 and for either or both of y = +/-inf and x = +/-inf (see Notes for specific values).

arctan2 is identical to the atan2 function of the underlying C library. The following special values are defined in the C standard:

x1	x2	arctan2(x1, x2)
+/- 0	+0	+/- 0
+/- 0	-0	+/- pi
> 0	+/-inf	+0 / +pi
< 0	+/-inf	-0 / -pi
+/-inf	+inf	+/- (pi/4)
+/-inf	-inf	+/- (3*pi/4)

Note that +0 and -0 are distinct floating point numbers, as are +inf and -inf.

Added in version 3.16.0.

See also

arctan, tan

Parameters:

x1: array_like

Y coordinates.

x2: array_like

X coordinates. x1 and x2 must be broadcastable to a common shape (which becomes the shape of the output). If both x1 and x2 have units, they must be equal or equivalent, in which case they will be conformed.

Returns:

Data

Array of angles in radians, in the range (-pi, pi].

Examples

>>> import numpy as np
>>> x = cf.Data([-1, +1, +1, -1])
>>> y = cf.Data([-1, -1, +1, +1])
>>> print((cf.Data.arctan2(y, x) * 180 / np.pi).array)
[-135.0 -45.0 45.0 135.0]
>>> x[1] = cf.masked
>>> y[1] = cf.masked
>>> print((cf.Data.arctan2(y, x) * 180 / np.pi).array)
[-135.0 -- 45.0 135.0]

>>> print(cf.Data.arctan2([0, 0, np.inf], [+0., -0., np.inf]).array)
[0.0 3.141592653589793 0.7853981633974483]

>>> print((cf.Data.arctan2([1, -1], [0, 0]) * 180 / np.pi).array)
[90.0 -90.0]