How to draw a line with matplotlib

Question

I cannot find a way to draw an arbitrary line with matplotlib Python library   It allows to draw horizontal and vertical lines  with matplotlib pyplot axhline and matplotlib pyplot axvline  for example   but i do not see how to draw a line through two given points  x1  y1  and  x2  y2   Is there a way  Is there a simple way

User · Accepted Answer

As of matplotlib 3 3  you can do this with plt axline  x1  y1    x2  y2

User · Answer

Just want to mention another option here   You can compute the coefficients using numpy polyfit    and feed the coefficients to numpy poly1d    This function can construct polynomials using the coefficients  you can find more examples here  https   docs scipy org doc numpy-1 13 0 reference generated numpy poly1d html  Let s say  given two data points  -0 3  -0 5  and  0 8  0 8   import numpy as np import matplotlib pyplot as plt    compute coefficients coefficients   np polyfit  -0 3  0 8    -0 5  0 8   1      create a polynomial object with the coefficients polynomial   np poly1d coefficients     for the line to extend beyond the two points     create the linespace using the min and max of the x lim   I m using -1 and 1 here x axis   np linspace -1  1     compute the y for each x using the polynomial y axis   polynomial x axis   fig   plt figure   axes   fig add axes  0 1  0 1  1  1   axes set xlim -1  1  axes set ylim -1  1  axes plot x axis  y axis  axes plot -0 3  -0 5  0 8  0 8  marker  o   color  red       Hope it helps

User · Answer

This will draw a line that passes through the points  -1  1  and  12  4   and another one that passes through the points  1  3  et  10  2   x1 are the x coordinates of the points for the first line  y1 are the y coordinates for the same -- the elements in x1 and y1 must be in sequence   x2 and y2 are the same for the other line   import matplotlib pyplot as plt x1  y1    -1  12    1  4  x2  y2    1  10    3  2  plt plot x1  y1  x2  y2  marker    o   plt show       I suggest you spend some time reading   studying the basic tutorials found on the very rich matplotlib website to familiarize yourself with the library   What if I don t want line segments   There are no direct ways to have lines extend to infinity    matplotlib will either resize rescale the plot so that the furthest point will be on the boundary and the other inside  drawing line segments in effect  or you must choose points outside of the boundary of the surface you want to set visible  and set limits for the x and y axis   As follows   import matplotlib pyplot as plt x1  y1    -1  12    1  10  x2  y2    -1  10    3  -1  plt xlim 0  8   plt ylim -2  8  plt plot x1  y1  x2  y2  marker    o   plt show

User · Answer

I was checking how ax axvline does work  and I ve written a small function that resembles part of its idea   import matplotlib pyplot as plt import matplotlib lines as mlines  def newline p1  p2       ax   plt gca       xmin  xmax   ax get xbound        if p2 0     p1 0            xmin   xmax   p1 0          ymin  ymax   ax get ybound       else          ymax   p1 1   p2 1 -p1 1    p2 0 -p1 0    xmax-p1 0           ymin   p1 1   p2 1 -p1 1    p2 0 -p1 0    xmin-p1 0        l   mlines Line2D  xmin xmax    ymin ymax       ax add line l      return l   So  if you run the following code you will realize how does it work  The line will span the full range of your plot  independently on how big it is   and the creation of the line doesn t rely on any data point within the axis  but only in two fixed points that you need to specify   import numpy as np x   np linspace 0 10  y   x  2  p1    1 20  p2    6 70   plt plot x  y  newline p1 p2  plt show

[python] How to draw a line with matplotlib?

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