Re: [Matplotlib-users] MultipleLocator and MaxNLocator

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Tommy,

I'm sorry. I forgot to hit send all *again*. Below is my original message,
but the function I wrote is updated because it wasn't exactly correct....

Ah. I was working on something to help out, so I'm just seeing Eric's very
elegant solution, which I have yet to try. However, I feel like you might
run into some problems if you always drop the first tick. For example, try
this plot:
______________
import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
import numpy as np
xs = np.linspace(2,12,1000)
ys = np.sin(xs)
n = 5
fig = plt.figure()
ax1 = fig.add_subplot(111)
ax1.plot(xs, ys)
ax1.xaxis.set_major_locator(MultipleLocator(5))
plt.show()
_____________
In this case, dropping the first tick will result in only one tick on the
screen.

What is your use-case? Are you annoyed that the axis labels are overlapping
at the far left? If that's the case, here's a little function (trimticks)
that I whipped up that might help. It drops the far left or far right label
if it is exactly at the edge of the axes. Should work for y axes as well.
_____________
def trimticks(ax, n=5):
    xmin, xmax = ax.get_xlim()
    if xmin%n == 0:
        xmin = xmin+n
    else:
        xmin = xmin + n - xmin%n

    if not xmax%n == 0:
        xmax = xmax + n - xmax%n

    ticks = np.arange(xmin, xmax, n)
    ax.set_xticks(ticks)

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
import numpy as np
xs = np.linspace(0,20,10000)
ys = np.sin(xs)
fig = plt.figure()
ax1 = fig.add_subplot(111)
ax1.plot(xs, ys)
trimticks(ax1)
plt.show()

___________________

On Sat, Feb 14, 2015 at 1:45 PM, Tommy Carstensen <
tom...@gm...> wrote:

> Erik, that doesn't seem to work either. I tried this:
>
> import matplotlib.pyplot as plt
> from matplotlib.ticker import MultipleLocator
> class TrimmedMultipleLocator(MultipleLocator):
>      def tick_values(self, vmin, vmax):
>          return MultipleLocator.tick_values(self, vmin, vmax)[2:]
> fig = plt.figure()
> ax1 = fig.add_subplot(111)
> ax1.xaxis.set_major_locator(TrimmedMultipleLocator(5))
> #xticks[0].label1.set_visible(False)
> #xticks[-1].label1.set_visible(False)
> #ax1.set_xticks(ax1.xaxis.get_major_ticks()[1:-1])
> ax1.plot(list(range(21)))
> plt.show()
>
> Here is an example of the use of prune='lower', but it does not allow
> one to set the tick step size:
>
> http://stackoverflow.com/questions/9422587/overlapping-y-axis-tick-label-and-x-axis-tick-label-in-matplotlib
>
> I think my best bet is to just set those ticks manually.
>
> On Sat, Feb 14, 2015 at 6:19 PM, Eric Firing <ef...@ha...> wrote:
> > On 2015/02/14 7:33 AM, Tommy Carstensen wrote:
> >> Thanks again Ryan. That's exactly what I want to achieve; i.e. remove
> >> the tick at 0 and only keep 5 and 10. Your solution works, but it's a
> >> bit of hack to use magic constants. I could however get those values
> >> from the xlim.
> >>
> >> Eric, I would describe the desired tick placement algorithm as
> >> removing the first tick on the axis. It can be achieved like this:
> >> ax1.xaxis.set_major_locator(MaxNLocator(prune='lower'))
> >
> > Aha! The problem is that the MaxNLocator is the only one with the prune
> > kwarg.  It could be added to the MultipleLocator.  For now, though, you
> > can make your own specialized Locator, hardwired to omit the first tick,
> > like this:
> >
> > from matplotlib.ticker import MultipleLocator
> >
> > class TrimmedMultipleLocator(MultipleLocator):
> >      def tick_values(self, vmin, vmax):
> >          return MultipleLocator.tick_values(self, vmin, vmax)[1:]
> >
> > then just use
> >
> > ax1.xaxis.set_major_locator(TrimmedMultipleLocator(5))
> >
> > I haven't tested it--but give it a try.  What it is doing is making a
> > subclass of MultipleLocator, and altering only the one little bit of its
> > behavior that you want to modify.  Everything else is automatically
> > inherited from the base class, MultipleLocator.
> >
> > Eric
> >
> >
> >>
> >> But that then overrides this:
> >> ax1.xaxis.set_major_locator(MultipleLocator(5))
> >>
> >> On Sat, Feb 14, 2015 at 5:27 PM, Ryan Nelson <rne...@gm...>
> wrote:
> >>> Tommy, (Sorry for the doubleup. I just realized I forgot to hit
> reply-all.)
> >>>
> >>> Do you want to remove the tick at 0 and only have 5,10, etc.? Could
> you just
> >>> do something like this instead:
> >>>
> >>> import matplotlib.pyplot as plt
> >>> from matplotlib.ticker import MultipleLocator
> >>> fig = plt.figure()
> >>> ax1 = fig.add_subplot(111)
> >>> ax1.set_xticks(range(5,11,5))
> >>> ax1.plot(range(11))
> >>> plt.show()
> >>>
> >>> Ryan
> >>>
> >>>
> >>> On Sat, Feb 14, 2015 at 10:47 AM, Tommy Carstensen
> >>> <tom...@gm...> wrote:
> >>>>
> >>>> Thanks for you answer Eric. I had to get some sleep before trying out
> >>>> things. I currently have the code below, but it does not remove the
> >>>> zero value tick. It removes the tick at 5 and 10 however.
> >>>>
> >>>> import matplotlib.pyplot as plt
> >>>> from matplotlib.ticker import MultipleLocator
> >>>> fig = plt.figure()
> >>>> ax1 = fig.add_subplot(111)
> >>>> ax1.xaxis.set_major_locator(MultipleLocator(5))
> >>>> xticks = ax1.xaxis.get_major_ticks()
> >>>> #xticks[0].label1.set_visible(False)
> >>>> #xticks[-1].label1.set_visible(False)
> >>>> ax1.set_xticks(ax1.get_xticks()[1:-1])
> >>>> ax1.plot(list(range(11)))
> >>>> plt.show()
> >>>>
> >>>> On Sat, Feb 14, 2015 at 2:01 AM, Eric Firing <ef...@ha...>
> wrote:
> >>>>> On 2015/02/13 3:29 PM, Tommy Carstensen wrote:
> >>>>>> Is it possible to combine MultipleLocator and MaxNLocator? One seems
> >>>>>> to erase the effect of the other.
> >>>>>
> >>>>> They are for different situations.  MultipleLocator is for when you
> know
> >>>>> what you want your tick interval to be; MaxNLocator is for when you
> >>>>> don't know that, but you do know roughly how many ticks you want, and
> >>>>> what sort of numerical intervals are acceptable.
> >>>>>
> >>>>> Eric
> >>>>>
> >>>>>
> >>>>>
> >>>>>
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