How to draw vertical lines on a given plot in matplotlib

Question

Given a plot of signal in time representation  how to draw lines marking corresponding time index   Specifically  given a signal plot with time index ranging from 0 to 2 6 s   I want to draw vertical red lines indicating corresponding time index for the list  0 22058956  0 33088437  2 20589566   how can I do it

User · Accepted Answer

The standard way to add vertical lines that will cover your entire plot window without you having to specify their actual height is plt.axvline

import matplotlib.pyplot as plt

plt.axvline(x=0.22058956)
plt.axvline(x=0.33088437)
plt.axvline(x=2.20589566)

OR

xcoords = [0.22058956, 0.33088437, 2.20589566]
for xc in xcoords:
    plt.axvline(x=xc)

You can use many of the keywords available for other plot commands (e.g. color, linestyle, linewidth ...). You can pass in keyword arguments ymin and ymax if you like in axes corrdinates (e.g. ymin=0.25, ymax=0.75 will cover the middle half of the plot). There are corresponding functions for horizontal lines (axhline) and rectangles (axvspan).

User · Answer

In addition to the plt axvline and plt plot  x1  x2    y1  y2   OR plt plot  x1  x2    y1  y2   as provided in the answers above  one can also use  plt vlines x pos  ymin y1  ymax y2    to plot a vertical line at x pos spanning from y1 to y2 where the values y1 and y2 are in absolute data coordinates

User · Answer

For multiple lines  xposition    0 3  0 4  0 45  for xc in xposition      plt axvline x xc  color  k   linestyle  --

User · Answer

matplotlib pyplot vlines vs  matplotlib pyplot axvline  The difference is that vlines accepts 1 or more locations for x  while axvline permits one location   Single location  x 37 Multiple locations  x  37  38  39    vlines takes ymin and ymax as a position on the y-axis  while axvline takes ymin and ymax as a percentage of the y-axis range   When passing multiple lines to vlines  pass a list to ymin and ymax    If you re plotting a figure with something like fig  ax   plt subplots    then replace plt vlines or plt axvline with ax vlines or ax axvline  respectively   import numpy as np import matplotlib pyplot as plt  xs   np linspace 1  21  200   plt figure figsize  10  7      only one line may be specified  full height plt axvline x 36  color  b   label  axvline - full height      only one line may be specified  ymin  amp  ymax spedified as a percentage of y-range plt axvline x 36 25  ymin 0 05  ymax 0 95  color  b   label  axvline -   of full height      multiple lines all full height plt vlines x  37  37 25  37 5   ymin 0  ymax len xs   colors  purple   ls  --   lw 2  label  vline multiple - full height      multiple lines with varying ymin and ymax plt vlines x  38  38 25  38 5   ymin  0  25  75   ymax  200  175  150   colors  teal   ls  --   lw 2  label  vline multiple - partial height      single vline with full ymin and ymax plt vlines x 39  ymin 0  ymax len xs   colors  green   ls      lw 2  label  vline single - full height      single vline with specific ymin and ymax plt vlines x 39 25  ymin 25  ymax 150  colors  green   ls      lw 2  label  vline single - partial height      place legend outside plt legend bbox to anchor  1 0  1   loc  upper left    plt show

User · Answer

Calling axvline in a loop  as others have suggested  works  but can be inconvenient because  Each line is a separate plot object  which causes things to be very slow when you have many lines  When you create the legend each line has a new entry  which may not be what you want   Instead you can use the following convenience functions which create all the lines as a single plot object  import matplotlib pyplot as plt import numpy as np   def axhlines ys  ax None  lims None    plot kwargs        quot  quot  quot      Draw horizontal lines across plot      param ys  A scalar  list  or 1D array of vertical offsets      param ax  The axis  or none to use gca       param lims  Optionally the  xmin  xmax  of the lines      param plot kwargs  Keyword arguments to be passed to plot      return  The plot object corresponding to the lines       quot  quot  quot      if ax is None          ax   plt gca       ys   np array  ys    if np isscalar ys  else ys  copy False      if lims is None          lims   ax get xlim       y points   np repeat ys    None   repeats 3  axis 1  flatten       x points   np repeat np array lims    np nan     None      repeats len ys   axis 0  flatten       plot   ax plot x points  y points  scalex   False    plot kwargs      return plot   def axvlines xs  ax None  lims None    plot kwargs        quot  quot  quot      Draw vertical lines on plot      param xs  A scalar  list  or 1D array of horizontal offsets      param ax  The axis  or none to use gca       param lims  Optionally the  ymin  ymax  of the lines      param plot kwargs  Keyword arguments to be passed to plot      return  The plot object corresponding to the lines       quot  quot  quot      if ax is None          ax   plt gca       xs   np array  xs    if np isscalar xs  else xs  copy False      if lims is None          lims   ax get ylim       x points   np repeat xs    None   repeats 3  axis 1  flatten       y points   np repeat np array lims    np nan     None      repeats len xs   axis 0  flatten       plot   ax plot x points  y points  scaley   False    plot kwargs      return plot

User · Answer

If someone wants to add a legend and or colors to some vertical lines  then use this     import matplotlib pyplot as plt    x coordinates for the lines xcoords    0 1  0 3  0 5    colors for the lines colors     r   k   b    for xc c in zip xcoords colors       plt axvline x xc  label  line at x       format xc   c c   plt legend   plt show       Results

[python] How to draw vertical lines on a given plot in matplotlib

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