C Library Functions - cartesian_to_polar (3)

NAME

cartesian_to_polar(3f) - [M_units:TRIGONOMETRY] convert Cartesian coordinates to polar coordinates (LICENSE:PD)

Synopsis
Description
Options
Results
Examples
Author
License

SYNOPSIS

subroutine cartesian_to_polar(x,y,radius,inclination)
     real,intent(in)  :: x,y
     real,intent(out) :: radius,inclination
subroutine cartesian_to_polar(xy,radius,inclination)
     complex,intent(in) :: xy
     real,intent(out) :: radius,inclination

DESCRIPTION

Convert a cartesian point <X,Y> to polar coordinates <radius, inclination> with angles in radians equivalent to using the formulas
       radius=sqrt(x**2+y**2)
       inclination=atan2(y,x)
where if inclination is negative, add PI.

OPTIONS

X The distance along the x-axis

Y The distance along the y-axis

XY Alternatively to using X and Y a complex value may be used. The real component will be treated as the X coordinate, and the imaginary component defines the Y coordinate of the input point.

If the input point <0.0,0.0> is used the inclination is arbitrarily returned as zero.

RESULTS

RADIUS The radial distance from the origin (O) to the point <X,Y>. If it exceeds huge(0.0), (-1)-huge(0.0) is returned.

INCLINATION
The inclination angle in radians between the inclination reference direction (x-axis) and the orthogonal projection of the line OP of the reference plane (x-y plane) in the range 0 <= INCLINATION < 2*PI radians. If the radius value exceeds huge(0) -1 is returned, else zero (0) is returned if no error occurs.

EXAMPLES

sample program:

   program demo_cartesian_to_polar
   use M_units, only : cartesian_to_polar
   ! basic cardinal directions
      call  printme( +1.0, +0.0)
      call  printme( +0.0, +1.0)
      call  printme( -1.0, +0.0)
      call  printme( +0.0, -1.0)
   ! the 3-4-5 right triangle
      call  printme( +4.0, +3.0)
      call  printme( +3.0, +4.0)
      call  printme( -3.0, +4.0)
      call  printme( -4.0, +3.0)
      call  printme( -4.0, -3.0)
      call  printme( -3.0, -4.0)
      call  printme( +3.0, -4.0)
      call  printme( +4.0, -3.0)
      write(*,’(*(g0))’) ’cases where input is too large:’
      call  printme( huge(0.0),huge(0.0))
      stopit: block
         real :: radius, inclination
         call cartesian_to_polar( huge(0.0), huge(0.0), radius, inclination)
      endblock stopit
   contains
   subroutine printme(x,y)
   real,intent(in):: x,y
   real :: radius,inclination
   integer :: ierr
      call cartesian_to_polar(x,y,radius,inclination,ierr)
      write(*,*)ierr, x,y,radius,inclination,inclination*180/acos(-1.0)
   end subroutine printme
   end program demo_cartesian_to_polar

Results:

> 0 1.00000000 0.00000000 1.00000000 0.00000000 0.00000000 > 0 0.00000000 1.00000000 1.00000000 1.57079637 90.0000000 > 0 -1.00000000 0.00000000 1.00000000 3.14159274 180.000000 > 0 0.00000000 -1.00000000 1.00000000 4.71238899 270.000000 > 0 4.00000000 3.00000000 5.00000000 0.643501103 36.8698959 > 0 3.00000000 4.00000000 5.00000000 0.927295208 53.1301003 > 0 -3.00000000 4.00000000 5.00000000 2.21429753 126.869896 > 0 -4.00000000 3.00000000 5.00000000 2.49809170 143.130096 > 0 -4.00000000 -3.00000000 5.00000000 3.78509378 216.869904 > 0 -3.00000000 -4.00000000 5.00000000 4.06888771 233.130081 > 0 3.00000000 -4.00000000 5.00000000 5.35589027 306.869904 > 0 4.00000000 -3.00000000 5.00000000 5.63968420 323.130096 > cases where input is too large: > 1 3.40282347E+38 3.40282347E+38 -3.40282347E+38 0.785398185 45.0000000 > STOP <ERROR> *cartesian_to_polar* overflow. radius=0.48123190965235028E+39

AUTHOR

John S. Urban

LICENSE

Public Domain

Nemo Release 3.1

cartesian_to_polar (3)

February 23, 2025

Generated by manServer 1.08 from dcc14b4e-49fd-45b8-90b2-ce2ddc577fe5 using man macros.

X	The distance along the x-axis
Y	The distance along the y-axis
XY	Alternatively to using X and Y a complex value may be used. The real component will be treated as the X coordinate, and the imaginary component defines the Y coordinate of the input point.

RADIUS	The radial distance from the origin (O) to the point <X,Y>. If it exceeds huge(0.0), (-1)-huge(0.0) is returned.
INCLINATION
	The inclination angle in radians between the inclination reference direction (x-axis) and the orthogonal projection of the line OP of the reference plane (x-y plane) in the range 0 <= INCLINATION < 2*PI radians. If the radius value exceeds huge(0) -1 is returned, else zero (0) is returned if no error occurs.