> From: C M [mailto:cmpyt...@gmail.com]
> Sent: Wednesday, February 03, 2010 21:59
>
> I'm using autoscale_view for the y axis, but find with a marker size >
> about 10, it will autoscale the graphs such that some markers are
> bisected by the edges of the frame. I already have it set to:
>
> self.subplot.autoscale_view(tight=False, scalex=False,
> scaley=True)
>
> so I'd basically like "tight" here to be "even less tight". For
> example, for a graph of time in minutes along the y axis, I'd like the
> bottom of the graph to actually be a bit below zero to catch events
> that are 0.5 min, etc., without them being half-buried under the edge
> of the graph.
>
> Can autoscale_view be altered a bit to allow for a more generous view?
For a similar requirement, I made the following custom locator:
----
import numpy as np
import matplotlib as mpl
import matplotlib.ticker as mticker
import matplotlib.transforms as mtransforms
class LooseMaxNLocator(mticker.MaxNLocator):
def __init__(self, margin = 0.05, **kwargs):
mticker.MaxNLocator.__init__(self, **kwargs)
self._margin = margin
def autoscale(self):
dmin, dmax = self.axis.get_data_interval()
if self._symmetric:
maxabs = max(abs(dmin), abs(dmax))
dmin = -maxabs
dmax = maxabs
dmin, dmax = mtransforms.nonsingular(dmin, dmax, expander = 0.05)
margin = self._margin * (dmax - dmin)
vmin = dmin - margin
vmax = dmax + margin
bin_boundaries = self.bin_boundaries(vmin, vmax)
vmin = min(vmin, max(bin_boundaries[bin_boundaries <= dmin]))
vmax = max(vmax, min(bin_boundaries[bin_boundaries >= dmax]))
return np.array([vmin, vmax])
----
The *margin* argument controls the looseness. For a given axis *ax*, you
instantiate and apply the locator with something like
ax.xaxis.set_major_locator(LooseMaxNLocator(nbins=7, steps=[1, 2, 5, 10]))
and likewise for the Y axis. I believe that if the plot has already been
drawn, you have to somehow force an autoscaling.
I wrote that about 1.5 years ago for an earlier version of matplotlib, and I
don't know how compatible it is with the current ticker.py code. In
particular, you might need to override *view_limits* instead of *autoscale*.
Anyway, I hope it's useful to you.
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