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?
6 Answers
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).
For multiple lines
xposition = [0.3, 0.4, 0.45]
for xc in xposition:
plt.axvline(x=xc, color='k', linestyle='--')
matplotlib.pyplot.vlines vs. matplotlib.pyplot.axvline
- The difference is that
vlinesaccepts 1 or more locations forx, whileaxvlinepermits one location.- Single location:
x=37 - Multiple locations:
x=[37, 38, 39]
- Single location:
vlinestakesyminandymaxas a position on the y-axis, whileaxvlinetakesyminandymaxas a percentage of the y-axis range.- When passing multiple lines to
vlines, pass alisttoyminandymax.
- When passing multiple lines to
- Also
matplotlib.axes.Axes.vlinesandmatplotlib.axes.Axes.axvlinefor the object oriented api.- If you're plotting a figure with something like
fig, ax = plt.subplots(), then replaceplt.vlinesorplt.axvlinewithax.vlinesorax.axvline, respectively.
- If you're plotting a figure with something like
- See this answer for horizontal lines with
.hlines
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 & ymax specified 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()
