It sounds like you were using the right approach, you just got a bit lost
on what some of the keyword parameters to annotate, etc do.
Here's an example that should do what you want:
import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
fig, ax = plt.subplots()
# Set the axis limits as you wanted...
ax.set_ylim([-0.6, 1.1])
# Set major and minor tick intervals
# We could just set the tick locations manually, but this way you'll keep
the
# same intervals when you zoom/pan/etc.
ax.yaxis.set_major_locator(MultipleLocator(1))
ax.yaxis.set_minor_locator(MultipleLocator(0.1))
# Make the bottom spine "float" instead of being at the bottom of the plot
ax.spines['bottom'].set_position(('data', 0))
# Hide the top and right spines (Similar to your sketch)
for position in ['right', 'top']:
ax.spines[position].set_visible(False)
# Turn off the top, right, and bottom major and minor ticks (as in your
sketch)
ax.tick_params(which='both', top=False, right=False, bottom=False,
labelbottom=False)
# Draw a 15 point long arrow that will always be at the top-left corner of
# the axes. The key is that we're specifying a location of (0,1) in
# "axes fraction" coordinates. We then place an empty text string 15
_points_
# above this (the `xytext` parameter controls the amount, `textcoords`
controls
# how it's interpreted). Then, we draw an arrow connecting the top left
corner
# of the axes to the (empty and not drawn) text string.
ax.annotate('', xy=(0,1), xycoords='axes fraction', xytext=(0,15),
textcoords='offset points', ha='center',
arrowprops=dict(arrowstyle='<|-', shrinkA=0, shrinkB=0,
facecolor='black'))
plt.show()
Hope that helps!
-Joe
On Fri, Jun 15, 2012 at 7:34 AM, Asbach, Mark <
mark.asb...@iais.fraunhofer.de> wrote:
> Hi there,
>
> I'm sorry to ask such a newbie question, but I'd like to format a custom
> box plot and although there are numerous examples on the web and tons of
> docstrings in matplotlib, I'm stuck somehow. My problems center around axes
> / spines. In detail, my problems are:
>
> 1) I want an y-axis on the left that spans from -0.6 to 1.1, ends in an
> arrow, has major ticks at 0 and 1 and minor ticks at [0.1...0.9]
> As far as I understand, there is no option to let spines end in an arrow
> head, so I have to draw the myself. I get the ticks to appear at the right
> positions and the y-range to be as desired - however, the spine line is not
> drawn over the full y-range, but only where there is data in the diagram.
> Also, I copied the arrow annotation code blindly from an older post on this
> list, but do not understand how I can adapt the arrow head to appear at a
> data position (instead of at the corner of the Axes area). One problem is,
> that I get ticks on the right although that spine was disabled.
>
> 2) I want some kind of x-axis at y==0, without ticks and without arrow
> Using some methods on the spines, I can disable the top spine and move the
> bottom spine to zero. However, as with the y-axis, I cannot control from
> where to where the line itself is drawn.
>
> As attachments, you'll find a hand sketch of what my graph should look
> like and matplotlib code that goes nearly all the way.
>
> I would be very happy about a hint on how to fix the problems left.
>
> Thanks an advance,
> Mark
>
>
>
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