Elemental Intrinsic Function (Generic): Produces an arctangent (inverse tangent). The result is the principal value of the argument of the nonzero complex number (x, y).
result = ATAN2 (y,x)
y |
(Input) Must be of type real. |
x |
(Input) Must have the same type and kind parameters as y. If y has the value zero, x cannot have the value zero. |
Results
The result type and kind is the same as x and is expressed in radians. The value lies in the range -pi <= ATAN2 (y, x) <= pi.
If x is not zero, the result is approximately equal to the value of arctan (y/ x).
If y > zero, the result is positive.
If y < zero, the result is negative.
If y is zero and x > zero, the result is y (so for x>0, ATAN2 ((+0.0), x) is +0.0 and ATAN2 ((-0.0), x) is -0.0).
If y is a positive real zero and x < zero, the result is pi.
If y is a negative real zero and x < zero, the result is -pi.
If x is a positive real zero, the result is pi/2.
If y is a negative real zero, the result is -pi/2.
Specific Name |
Argument Type |
Result Type |
|---|---|---|
ATAN2 |
REAL(4) |
REAL(4) |
DATAN2 |
REAL(8) |
REAL(8) |
QATAN2 |
REAL(16) |
REAL(16) |
Example
ATAN2 (2.679676, 1.0) has the value 1.213623.
If Y is an array that has the value
[ 1 1 ] [ -1 -1 ]
and X is an array that has the value
[ -1 1 ] [ -1 1 ],
then ATAN2 (Y, X) is
