Plotting lines connecting points

Question

I know there is another very similar question  but I could not extract the information I need from it   plotting lines in pairs  I have 4 points in the  x y  plane  x  x1 x2 x3 x4  and y  y1 y2 y3 y4   x  -1  0 5  1 -0 5  y   0 5   1  -0 5  -1    Now  I can plot the four points by doing   import matplotlib pyplot as plt  plt plot x y   ro   plt axis  equal   plt show     But  apart from the four points  I would like to have 2 lines   1  one connecting  x1 y1  with  x2 y2  and  2  the second one connecting  x3 y3  with  x4 y4    This is a simple toy example  In the real case I have 2N points in the plane   How can I get the desired output  for points with two connecting lines    Thank you

User · Answer

I realize this question was asked and answered a long time ago, but the answers don't give what I feel is the simplest solution. It's almost always a good idea to avoid loops whenever possible, and matplotlib's plot is capable of plotting multiple lines with one command. If x and y are arrays, then plot draws one line for every column.

In your case, you can do the following:

x=np.array([-1 ,0.5 ,1,-0.5])
xx = np.vstack([x[[0,2]],x[[1,3]]])
y=np.array([ 0.5,  1, -0.5, -1])
yy = np.vstack([y[[0,2]],y[[1,3]]])
plt.plot(xx,yy, '-o')

Have a long list of x's and y's, and want to connect adjacent pairs?

xx = np.vstack([x[0::2],x[1::2]])
yy = np.vstack([y[0::2],y[1::2]])

Want a specified (different) color for the dots and the lines?

plt.plot(xx,yy, '-ok', mfc='C1', mec='C1')

User · Answer

Use the matplotlib arrow   function and set the parameters head length and head width to zero to don t get an  arrow-end    The connections between the different points can be simply calculated using vector addition with  A    1 2   B  3 4  --  Connection between A and B is B-A    2 2    Drawing this vector starting at the tip of A ends at the tip of B    import numpy as np import matplotlib pyplot as plt from matplotlib import style style use  fivethirtyeight     A   np array   10 8   1 2   7 5   3 5   7 6   8 7   9 9   4 5   6 5   6 8      fig   plt figure figsize  10 10   ax0   fig add subplot 212   ax0 scatter A   0  A   1     ax0 arrow A 0  0  A 0  1  A 1  0 -A 0  0  A 1  1 -A 0  1  width 0 02 color  red  head length 0 0 head width 0 0  ax0 arrow A 2  0  A 2  1  A 9  0 -A 2  0  A 9  1 -A 2  1  width 0 02 color  red  head length 0 0 head width 0 0  ax0 arrow A 4  0  A 4  1  A 6  0 -A 4  0  A 6  1 -A 4  1  width 0 02 color  red  head length 0 0 head width 0 0    plt show

User · Answer

I think you re going to need separate lines for each segment   import numpy as np import matplotlib pyplot as plt  x  y   np random random size  2 10    for i in range 0  len x   2       plt plot x i i 2   y i i 2    ro-    plt show      The numpy import is just to set up some random 2x10 sample data

User · Answer

You can just pass a list of the two points you want to connect to plt plot  To make this easily expandable to as many points as you want  you could define a function like so   import matplotlib pyplot as plt  x  -1  0 5  1 -0 5  y   0 5   1  -0 5  -1   plt plot x y   ro    def connectpoints x y p1 p2       x1  x2   x p1   x p2      y1  y2   y p1   y p2      plt plot  x1 x2   y1 y2   k-    connectpoints x y 0 1  connectpoints x y 2 3   plt axis  equal   plt show       Note  that function is a general function that can connect any two points in your list together   To expand this to 2N points  assuming you always connect point i to point i 1  we can just put it in a for loop   import numpy as np for i in np arange 0 len x  2       connectpoints x y i i 1    In that case of always connecting point i to point i 1  you could simply do   for i in np arange 0 len x  2       plt plot x i i 2  y i i 2   k-

[matplotlib] Plotting lines connecting points

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