Down arrow symbol in matplotlib

Question

I would like to create a graph in which some points have a down arrow (see image below). In astronomy, this illustrates that the true value is actually less than the measured value. Please note that only some of the dots have this symbol.

I would like to know how I can create such characters in matplotlib. Are there down arrows that I can use?

Thanks for your help in advance!

Answer 1

Sure.

When calling the plot matplotlibs function, set marker

• If things like caretdown don't work for you, you can create your own token by passing a list of pairs (x, y) that are passed to the Path artist. x / y - 0 ... 1 normalized coordinates that scale to the set marker size.
• You can also pass an existing Path instance as a marker , which provides even more flexibility.
• As mentioned in the comments to tom10, you can also pass a string in the form of $…$ as a marker, where … is arbitrary text, including Unicode characters, if your font supports it (there should be a case of days). Unicode down arrow: ↓ (or \u2193 , which results in $\u2193$ as a marker. Note that this must be a unicode string in Python 2.x [preend u]). Unicode Block Arrows @Wikipedia
• You can also try passing the Arrow instance as a marker, but I'm not sure if this works.

Answer 2

The answer to my question was answered by Tom0 and Dom0. However, I just want to help beginners, like me, understand how to create these arrows. Below is the code that I found and edited to include the example and sentence in the above. Hope this helps people quickly understand. I am not looking for any items.

If you like the example, please thank Dom0, not me. :-)

 import numpy as np import matplotlib.pyplot as plt symbols = [u'\u2193'] # this helps you get the symbol x = np.arange(10.) y = np.exp(-x/2.) plt.figure() for i, symbol in enumerate(symbols): y2 = np.exp(-x/2.) plt.plot(x, y, 'o') # plotting with field circles plt.plot(x, y2, 'g') # plotting with green line for x0, y0 in zip(x, y2): plt.text(x0, y0, symbol, fontname='STIXGeneral', size=30, va='center', ha='center', clip_on=True) plt.show() 

Answer 3

Take a look at this sample code: http://matplotlib.org/examples/pylab_examples/errorbar_limits.html

OR: Another easy way to do this:

 arrow = u'$\u2193$' ax.plot(x, y, linestyle='none', marker=arrow, markersize=10) 

Answer 4

Matplotlib supports a subset of Latex in a built-in module called mathtext. The main goal is to correctly display mathematical and scientific equations and symbols, but there is also a large number of arrow symbols that can be easily used in your graphs. The following is a link to a math expressions tutorial. At the bottom of the page is a list of approximately 80 arrow symbols.

https://matplotlib.org/users/mathtext.html#mathtext-tutorial

Examples:

 plt.plot(x, y, marker=r'$\uparrow$') plt.plot(x, y, marker=r'$\downarrow$')