Python conversion between coordinates

Question

Are there functions for conversion between different coordinate systems   For example  Matlab has  rho phi    cart2pol x y  for conversion from cartesian to polar coordinates  Seems like it should be in numpy or scipy

User · Answer

Thinking about it in general  I would strongly consider hiding coordinate system behind well-designed abstraction  Quoting Uncle Bob and his book   class Point object      def setCartesian self  x  y      def setPolar self  rho  theta      def getX self      def getY self      def getRho self      def setTheta self    With interface like that any user of Point class may choose convenient representation  no explicit conversions will be performed  All this ugly sines  cosines etc  will be hidden in one place  Point class  Only place where you should care which representation is used in computer memory

User · Answer

Using numpy  you can define the following   import numpy as np  def cart2pol x  y       rho   np sqrt x  2   y  2      phi   np arctan2 y  x      return rho  phi   def pol2cart rho  phi       x   rho   np cos phi      y   rho   np sin phi      return x  y

User · Answer

The existing answers can be simplified   from numpy import exp  abs  angle  def polar2z r theta       return r   exp  1j   theta    def z2polar z       return   abs z   angle z      Or even   polar2z   lambda r    r   exp  1j       z2polar   lambda z    abs z   angle z      Note these also work on arrays   rS  thetaS   z2polar   z1 z2 z3    zS   polar2z  rS  thetaS

User · Answer

If you can t find it in numpy or scipy  here are a couple of quick functions and a point class   import math  def rect r  theta          theta in degrees      returns tuple   float  float    x y              x   r   math cos math radians theta       y   r   math sin math radians theta       return x y  def polar x  y          returns r  theta degrees              r    x    2   y    2      5     theta   math degrees math atan2 y x       return r  theta  class Point object       def   init   self  x None  y None  r None  theta None              x and y or r and theta degrees                      if x and y              self c polar x  y          elif r and theta              self c rect r  theta          else              raise ValueError  Must specify x and y or r and theta       def c polar self  x  y  f   polar           self  x   x         self  y   y         self  r  self  theta   f self  x  self  y          self  theta radians   math radians self  theta      def c rect self  r  theta  f   rect              theta in degrees                     self  r   r         self  theta   theta         self  theta radians   math radians theta          self  x  self  y   f self  r  self  theta      def setx self  x           self c polar x  self  y      def getx self           return self  x     x   property fget   getx  fset   setx      def sety self  y           self c polar self  x  y      def gety self           return self  y     y   property fget   gety  fset   sety      def setxy self  x  y           self c polar x  y      def getxy self           return self  x  self  y     xy   property fget   getxy  fset   setxy      def setr self  r           self c rect r  self  theta      def getr self           return self  r     r   property fget   getr  fset   setr      def settheta self  theta              theta in degrees                     self c rect self  r  theta      def gettheta self           return self  theta     theta   property fget   gettheta  fset   settheta      def set r theta self  r  theta              theta in degrees                     self c rect r  theta      def get r theta self           return self  r  self  theta     r theta   property fget   get r theta  fset   set r theta      def   str   self           return           format self  x  self  y

User · Answer

If your coordinates are stored as complex numbers you can use cmath

User · Answer

There is a better way to write polar    here it is    def polar x y      returns r  theta degrees     return math hypot x y  math degrees math atan2 y x

User · Answer

You can use the cmath module    If the number is converted to a complex format  then it becomes easier to just call the polar method on the number   import cmath input num   complex 1  2    stored as 1 2j r  phi   cmath polar input num

[python] Python conversion between coordinates

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