Fortran Wiki
atan2
Description
atan2(y, x) computes the arctangent of the complex number .
This function can be used to transform from Cartesian into polar coordinates and allows to determine the angle in the correct quadrant. To convert from Cartesian Coordinates to polar coordinates :
Standard
FORTRAN 77 and later
Class
Syntax
result = atan2(y, x)Arguments
y- The type shall bereal.x- The type and kind type parameter shall be the same asy. Ifyis zero, thenxmust be nonzero.
Return value
The return value has the same type and kind type parameter as y. It is the principal value of the complex number . If x is nonzero, then it lies in the range . The sign is positive if y is positive. If y is zero, then the return value is zero if x is strictly positive, if x is negative and y is positive zero (or the processor does not handle signed zeros), and if x is negative and y is negative zero. Finally, if x is zero, then the magnitude of the result is .
Example
program test_atan2
real(4) :: x = 1.e0_4, y = 0.5e0_4
x = atan2(y,x)
end program test_atan2Note: In Return value, NNemec changed the first to . Joe Krahn reverted the edit, following the Fortran 2008 specs.