plot a circle with pyplot

Question

surprisingly I didn t find a straight-forward description on how to draw a circle with matplotlib pyplot  please no pylab  taking as input center  x y  and radius r  I tried some variants of this   import matplotlib pyplot as plt circle plt Circle  0 0  2    here must be something like circle plot   or not  plt show         but still didn t get it working

User · Answer

If you aim to have the  circle  maintain a visual aspect ratio of 1 no matter what the data coordinates are  you could use the scatter   method  http   matplotlib org 1 3 1 api pyplot api html matplotlib pyplot scatter      import matplotlib pyplot as plt x    1  2  3  4  5  y    10  20  30  40  50  r    100  80  60  40  20    in points  not data units fig  ax   plt subplots 1  1  ax scatter x  y  s r  fig show

User · Answer

If you want to plot a set of circles  you might want to see this post or this gist a bit newer   The post offered a function named circles   The function circles works like scatter  but the sizes of plotted circles are in data unit    Here s an example   from pylab import   figure figsize  8 8   ax subplot aspect  equal     plot one circle  the biggest one on bottom-right  circles 1  0  0 5   r   alpha 0 2  lw 5  edgecolor  b   transform ax transAxes    plot a set of circles  circles in diagonal  a arange 11  out   circles a  a  a 0 2  c a  alpha 0 5  edgecolor  none   colorbar out   xlim 0 10  ylim 0 10

User · Answer

import matplotlib pyplot as plt  circle1   plt Circle  0  0   0 2  color  r   plt gca   add patch circle1   A quick condensed version of the accepted answer  to quickly plug a circle into an existing plot  Refer to the accepted answer and other answers to understand the details  By the way   gca   means Get Current Axis

User · Answer

Similarly to scatter plot you can also use normal plot with circle line style  Using markersize parameter you can adjust radius of a circle   import matplotlib pyplot as plt  plt plot 200  2   o   markersize 7

User · Answer

Extending the accepted answer for a common usecase  In particular    View the circles at a natural aspect ratio  Automatically extend the axes limits to include the newly plotted circles    Self-contained example   import matplotlib pyplot as plt  fig  ax   plt subplots   ax add patch plt Circle  0  0   0 2  color  r   alpha 0 5   ax add patch plt Circle  1  1   0 5  color   00ffff   alpha 0 5   ax add artist plt Circle  1  0   0 5  color   000033   alpha 0 5     Use adjustable  box-forced  to make the plot area square-shaped as well  ax set aspect  equal   adjustable  datalim   ax plot      Causes an autoscale update  plt show     Note the difference between ax add patch     and ax add artist      of the two  only the former makes autoscaling machinery take the circle into account  reference  discussion   so after running the above code we get     See also  set aspect     documentation

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usr bin python import matplotlib pyplot as plt import numpy as np  def xy r phi     return r np cos phi   r np sin phi   fig   plt figure   ax   fig add subplot 111 aspect  equal      phis np arange 0 6 28 0 01  r  1  ax plot   xy r phis   c  r  ls  -    plt show     Or  if you prefer  look at the paths  http   matplotlib sourceforge net users path tutorial html

User · Answer

I see plots with the use of   circle  but based on what you might want to do you can also try this out   import matplotlib pyplot as plt import numpy as np  x   list range 1 6   y   list range 10  20  2    print x  y   for i  data in enumerate zip x y        j  k   data     plt scatter j k  marker    o   s     i 1   4  50  alpha   0 3      centers   np array   5 18    3 14    7 6    m  n   make blobs n samples 20  centers   5 18    3 14    7 6    n features 2   cluster std   0 4  colors     g    b    r    m    plt figure num None  figsize  7 6   facecolor  w   edgecolor  k   plt scatter m   0   m   1    for i in range len centers         plt scatter centers i 0   centers i 1   color   colors i   marker    o   s   13000  alpha   0 2      plt scatter centers i 0   centers i 1   color    k   marker    x   s   50   plt savefig  plot png

User · Answer

You need to add it to an axes  A Circle is a subclass of an Patch  and an axes has an add patch method   You can also use add artist but it s not recommended   Here s an example of doing this  import matplotlib pyplot as plt  circle1   plt Circle  0  0   0 2  color  r   circle2   plt Circle  0 5  0 5   0 2  color  blue   circle3   plt Circle  1  1   0 2  color  g   clip on False   fig  ax   plt subplots     note we must use plt subplots  not plt subplot    or if you have an existing figure    fig   plt gcf     ax   fig gca    ax add patch circle1  ax add patch circle2  ax add patch circle3   fig savefig  plotcircles png    This results in the following figure   The first circle is at the origin  but by default clip on is True  so the circle is clipped when ever it extends beyond the axes  The third  green  circle shows what happens when you don t clip the Artist  It extends beyond the axes  but not beyond the figure  ie the figure size is not automatically adjusted to plot all of your artists   The units for x  y and radius correspond to data units by default  In this case  I didn t plot anything on my axes  fig gca   returns the current axes   and since the limits have never been set  they defaults to an x and y range from 0 to 1  Here s a continuation of the example  showing how units matter  circle1   plt Circle  0  0   2  color  r     now make a circle with no fill  which is good for hi-lighting key results circle2   plt Circle  5  5   0 5  color  b   fill False  circle3   plt Circle  10  10   2  color  g   clip on False       ax   plt gca   ax cla     clear things for fresh plot    change default range so that new circles will work ax set xlim  0  10   ax set ylim  0  10     some data ax plot range 11    o   color  black     key data point that we are encircling ax plot  5    5    o   color  y        ax add patch circle1  ax add patch circle2  ax add patch circle3  fig savefig  plotcircles2 png    which results in   You can see how I set the fill of the 2nd circle to False  which is useful for encircling key results  like my yellow data point

User · Answer

Hello I have written a code for drawing a circle  It will help for drawing all kind of circles  The image shows the circle with radius 1 and center at 0 0 The center and radius can be edited of any choice      Draw a circle with center and radius defined    Also enable the coordinate axes import matplotlib pyplot as plt import numpy as np   Define limits of coordinate system x1   -1 5 x2   1 5 y1   -1 5 y2   1 5  circle1   plt Circle  0 0  1  color    k   fill   False  clip on   False  fig  ax   plt subplots   ax add artist circle1  plt axis  equal   ax spines  left   set position  zero   ax spines  bottom   set position  zero   ax spines  right   set color  none   ax spines  top   set color  none   ax xaxis set ticks position  bottom   ax yaxis set ticks position  left   plt xlim left x1  plt xlim right x2  plt ylim bottom y1  plt ylim top y2  plt axhline linewidth 2  color  k   plt axvline linewidth 2  color  k      plt grid True  plt grid color  k   linestyle  -    linewidth 0 5  plt show     Good luck

[python] plot a circle with pyplot

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