ATAN2(Y, X)
computes the principal value of the argument function of the complex number X + i Y. This function can be used to transform from Cartesian into polar coordinates and allows to determine the angle in the correct quadrant.
Fortran 77 and later
Elemental function
RESULT = ATAN2(Y, X)
Y | The type shall be REAL . |
X | The type and kind type parameter shall be the same as Y. If Y is zero, then X must be nonzero. |
The return value has the same type and kind type parameter as Y. It is the principal value of the complex number X + i Y. If X is nonzero, then it lies in the range -\pi \le \atan (x) \leq \pi. The sign is positive if Y is positive. If Y is zero, then the return value is zero if X is strictly positive, \pi if X is negative and Y is positive zero (or the processor does not handle signed zeros), and -\pi if X is negative and Y is negative zero. Finally, if X is zero, then the magnitude of the result is \pi/2.
program test_atan2 real(4) :: x = 1.e0_4, y = 0.5e0_4 x = atan2(y,x) end program test_atan2
Name | Argument | Return type | Standard |
ATAN2(X, Y) |
REAL(4) X, Y |
REAL(4) |
Fortran 77 and later |
DATAN2(X, Y) |
REAL(8) X, Y |
REAL(8) |
Fortran 77 and later |
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