Opened 11 years ago

# arrows on the end of axes

Reported by: Owned by: jason jason, was minor sage-6.4 graphics ppurka N/A

### Description

Here is a feature request from a post to the matplotlib mailing list: http://sourceforge.net/mailarchive/forum.php?thread_name=4D496F84.7070909%40nerim.fr&forum_name=matplotlib-users

I use matplolib by the mathematical system Sage in order to plot a function. The Sage code calls matplotlib and uses its options : The Sage command is

plot (sin, x, -5, 5)

I add labels par axes_labels or remove axes by :

plot (sin(x), x, -5, 5, axes_label = ['x', 'y']) plot (sin(x), x, -5, 5, axes=false)

French users (and maybe others) uses arrows and not lines for axes. I'm looking for a plot (sin(x), x, -5, 5, axes="arrows") Is there a pretty way to get these arrows. The result of this code isn't so fine. length, width and color don't match.

plot (sin(x), x, -5, 5, axes=false) + arrow ((-5,0),(5,0)) + arrow ((0,-1),(0,1))

What options do you propose ? I don't find relevant answers in the archive.

An answer gives some relevant matplotlib code that does this:

Hi Francois,

I'm not sure I understand - but do you want the arrows at the end of the axes spines? I don't think there's a direct way to adjust the spines to become arrows at the moment, but we can remedy that by making annotations in axes coordinates. The important thing to know here is that in axes coordinates, which are always between 0-1, spine endpoints are at these locations: (0,0), (0,1), (1,0), and (1,1). Here's the code, and attached is the resulting image

```  import matplotlib.pyplot as plt
ax = plt.subplot(1,1,1)

al = 7 # arrow length in points
arrowprops=dict(clip_on=False, # plotting outside axes on purpose
frac=1., # make end arrowhead the whole size of arrow
facecolor='k')
kwargs = dict(
xycoords='axes fraction',
textcoords='offset points',
arrowprops= arrowprops,
)

ax.annotate("",(1,0),xytext=(-al,0), **kwargs) # bottom spine arrow
ax.annotate("",(0,1),xytext=(0,-al), **kwargs) # left spin arrow

# hide the top and right spines
[sp.set_visible(False) for sp in ax.spines['top'],ax.spines['right']]

#hide the right and top tick marks
ax.yaxis.tick_left()
ax.xaxis.tick_bottom()

x = np.linspace(-5,5,50)
ax.plot(x, np.sin(x))

# adjust the view a little bit
ax.set_xlim(-5,5)
ax.set_ylim(-1.1,1.1)
plt.draw()
```

I'm not familiar with how SAGE exposes matplotlib functionality, though, since the syntax you used differs from how matplotlib is utilized.

best, -- Paul Ivanov

### comment:1 Changed 9 years ago by kcrisman

See also this ask.sagemath.org question. It would be nice for someone to implement e.g. `axes_arrows=True` or even `axes_arrows=[True,False]` for the different directions or something.

### comment:4 Changed 8 years ago by jdemeyer

• Milestone changed from sage-5.11 to sage-5.12

### comment:5 Changed 8 years ago by vbraun_spam

• Milestone changed from sage-6.1 to sage-6.2

### comment:6 Changed 8 years ago by vbraun_spam

• Milestone changed from sage-6.2 to sage-6.3

### comment:7 Changed 7 years ago by vbraun_spam

• Milestone changed from sage-6.3 to sage-6.4
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