On Sun, Mar 11, 2012 at 2:32 PM, Christopher Graves <
christoph.gra...@gmail.com> wrote:
> On Sun, Mar 11, 2012 at 2:06 PM, Mike Kaufman <mck...@gmail.com> wrote:
>
>> On 3/11/12 8:14 AM, cgraves wrote:
>>
>>>
>>> Hi, here is an example script which places minor ticks with 2 per major
>>> tick
>>> (minor tick spacing is "fractional" of major tick spacing with relative
>>> interval of 1/2):
>>>
>>> from pylab import *
>>> fig=figure()
>>> ax=subplot(111)
>>> ax.autoscale(tight=True)
>>> plot([1,2,4],[1,2,3])
>>> x_ticks_maj_spacing =
>>> float(abs(ax.xaxis.get_**ticklocs()[0]-ax.xaxis.get_**ticklocs()[1]))
>>> x_ticks_min_spacing = x_ticks_maj_spacing/2
>>> ax.xaxis.set_minor_locator(**MultipleLocator(x_ticks_min_**spacing))
>>> y_ticks_maj_spacing =
>>> float(abs(ax.yaxis.get_**ticklocs()[0]-ax.yaxis.get_**ticklocs()[1]))
>>> y_ticks_min_spacing = y_ticks_maj_spacing/2
>>> ax.yaxis.set_minor_locator(**MultipleLocator(y_ticks_min_**spacing))
>>> show()
>>>
>>> This works fine. However, if one changes the axes limits then the major
>>> ticks get automatically adjusted to a different interval but the minor
>>> ticks
>>> remain at the positions they were already at. To see this, either use the
>>> zoom tools or do the following after running the above:
>>>
>>> xlim(1,2.5)
>>> fig.canvas.draw()
>>>
>>> The question is, what is the best way to maintain the fractional minor
>>> tick
>>> spacing? I suppose one could set up a way to update the set_minor_locator
>>> and redraw the figure each time the figure axes limits are adjusted, but
>>> is
>>> there a better way?
>>>
>>
>> Try this:
>>
>> from pylab import *
>> from matplotlib.ticker import AutoMinorLocator
>>
>> clf()
>> ax=subplot(111)
>> ax.autoscale(tight=True)
>> plot([1,2,4],[1,2,3])
>> ax.xaxis.set_minor_locator(**AutoMinorLocator(2))
>> ax.yaxis.set_minor_locator(**AutoMinorLocator(2))
>> draw()
>>
>> M
>>
>> PS: I believe this is a fairly new feature...
>>
>
> Thanks! Great news that AutoMinorLocator has been added and accomplishes
> this. Regarding the P.S. I can confirm that the feature was not in
> matplotlib 1.0.1 - I had to update to 1.1.0 to use it.
>
> Best /Chris
>
Hi Mike,
A follow-up question... When using that, if one then tries to manually use
the zoom-box tool available with a matplotlib plot, if one draws too small
of a box (less than 2 major ticks in x or y dimension, based on the
following error message), it gives the following error and further
operations on the plot do not work.
ValueError: Need at least two major ticks to find minor tick locations
( File "/usr/lib/pymodules/python2.7/matplotlib/ticker.py", line 1528, in
__call__ )
Any way to avoid this for now? (And ultimately, should this be made into a
bug fix request?)
Best /Chris
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