python + matplotlib: how to insert more space between the axis and the tick labels in a polar chart?

Question

I'm trying to make a polar chart with matplotlib and python 2.7, but I'm struggling on how to increase the space between the X-Axis and the Tick Labels for that same axis. As you can see on the picture, the labels for 12:00 and 6:00 looks just fine, I wish the same space for all other labels.

I tried with

ax.xaxis.LABELPAD = 10

but it doesn't have any effect.

enter image description here

Here is my code (sorry for the mess....):

import numpy as np
import matplotlib as mpl
mpl.use('Agg')
import matplotlib.pyplot as plt
import matplotlib.dates
from matplotlib.dates import YearLocator, MonthLocator, DateFormatter
import matplotlib.cm as cm
import matplotlib.ticker as tkr
import pdb
def plot_clock(data,filename,path,**kwargs): # (x,y,colors,lab_x,lab_y,xTicks,filename,legend,**kwargs):
    bins = [0,0.5,1.5,2.5,3.5,4.5,5.5,6.5,7.5,8.5,9.5,10.5,11.5,12,12.5,13.5,14.5,15.5,16.5,17.5,18.5,19.5,20.5,21.5,22.5,23.5,23.999999];
    data = np.array(data)/(60*60)
    DATA_ = np.histogram(data,bins)[0]
    def hour_formatAM(x, p):
        #pdb.set_trace()
        if x > 0:
            return str(format(x*6/np.pi, "01.0f") + ':00')
        else:
            return '12:00'

    def hour_formatPM(x, p):
        #pdb.set_trace()
        if x > 0:
            return str(format(x*6/np.pi+12, "01.0f") + ':00')
        else:
            return '24:00'

    '''font = {'family' : 'normal',
        'weight' : 'bold',
        'size'   : 12}
    mpl.rc('font', **font)'''

    mpl.rcParams.update({'font.size': 8})
    #sub plot AM
    theta = np.array(bins[1:13]) * np.pi / 6
    radii =  DATA_[1:13]
    radii[-1] += DATA_[0]
    width = 1 * np.pi / 6

    fig = plt.figure(figsize=(5.5,3),dpi=600)
    ax = fig.add_subplot(121, polar=True)
    bars = ax.bar(theta, radii, width=width, bottom=0)
    ax.set_theta_offset(np.pi/2)
    ax.set_theta_direction(-1)

    ax.xaxis.set_ticks(np.arange(0, np.pi*2, np.pi/6))
    ax.get_xaxis().set_major_formatter(tkr.FuncFormatter(hour_formatAM))
    ax.yaxis.set_ticks(np.arange(1,max(DATA_),1))
    for t, bar in zip(theta, bars):
        bar.set_facecolor(plt.cm.jet(t / 12.))
        bar.set_alpha(0.5)


    #sub plot PM
    theta = np.array(bins[14:26]) * np.pi / 6
    radii =  DATA_[14:26]
    radii[-1] += DATA_[13]
    width = 1 * np.pi / 6

    ax = fig.add_subplot(122, polar=True)
    bars = ax.bar(theta, radii, width=width, bottom=0)
    ax.set_theta_offset(np.pi/2)
    ax.set_theta_direction(-1)
    pdb.set_trace()
    ax.xaxis.set_ticks(np.arange(0, np.pi*2, np.pi/6))
    ax.get_xaxis().set_major_formatter(tkr.FuncFormatter(hour_formatPM))
    ax.yaxis.set_ticks(np.arange(1,max(DATA_),1))
    for t, bar in zip(theta, bars):
        bar.set_facecolor(plt.cm.jet(t / 12.))
        bar.set_alpha(0.5) 
    #pdb.set_trace()
    #fig.tight_layout() 
    #xlabels = [item.get_text() for item in ax.get_xticklabels()]
    ax.xaxis.LABELPAD = 10 
    #[item.set_fontsize(12) for item in ax.xaxis.get_major_ticks()]

    fig.subplots_adjust(wspace = 0.4) # http://matplotlib.org/faq/howto_faq.html
    fig.savefig(path + filename,format='pdf')  


data = [ 10.49531611,  22.49511583,  10.90891806,  18.99525417,
        21.57165972,   6.687755  ,   6.52137028,  15.86534639,
        18.53823556,   6.32563583,  12.99365833,  11.06817056,
        17.29261306,  15.31288556,  19.16236667,  10.38483333,
        14.51442222,  17.01413611,   6.96102278,  15.98508611,
        16.5287    ,  15.26533889,  20.83520278,  17.21952056,
         7.3225775 ,  16.42534361,  14.38649722,  21.63573111,  16.19249444]
data = np.array(data)*60*60
plot_clock(data,'figure2_StartTime.pdf','./')

This may be of use: http://stackoverflow.com/questions/17159668/matplotlib-adding-padding-offset-to-polar-plots-tick-labels — dnf0, Nov 26 '13 at 16:36
Thanks, that indeed helped. with `ax.set_thetagrids(thetaticks, frac=1.2)` I'm able to fix the padding error, but it will pad all the ticks, also 12:00 and 6:00 which just looks nice as they are right now. — otmezger, Nov 26 '13 at 17:46
If you want to adjust on a per-label basis you either will have to do it by hand, or write some code to check if the text bounding box is overlapping with the axis. — tacaswell, Nov 26 '13 at 18:40

Joe Kington · Accepted Answer · 2013-11-26T19:37:34.360

@dabillox already mentioned using the frac kwarg to ax.set_thetagrids.

However, as you've noticed, what you're really wanting to change is the alignment of the ticklabels, rather than the overall radial displacement of the tick labels.

On a side note, the reason that labelpad had no effect is that it controls the padding between the axis label (e.g. plt.xlabel, plt.ylabel) and the axis, not the tick labels.

First off, you could write your example code a bit more cleanly. Here's more-or-less how I would approach what you're doing (note that this will still have the same problem with tick label positioning):

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as tkr

def main():
    data = [ 10.49531611,  22.49511583,  10.90891806,  18.99525417,
            21.57165972,   6.687755  ,   6.52137028,  15.86534639,
            18.53823556,   6.32563583,  12.99365833,  11.06817056,
            17.29261306,  15.31288556,  19.16236667,  10.38483333,
            14.51442222,  17.01413611,   6.96102278,  15.98508611,
            16.5287    ,  15.26533889,  20.83520278,  17.21952056,
             7.3225775 ,  16.42534361,  14.38649722,  21.63573111,  16.19249444]
    data = np.array(data)*60*60
    plot_clock(data)
    plt.show()

def plot_clock(data):
    def hour_formatAM(x, p):
        hour = x * 6 / np.pi
        return '{:0.0f}:00'.format(hour) if x > 0 else '12:00'

    def hour_formatPM(x, p):
        hour = x * 6 / np.pi
        return '{:0.0f}:00'.format(hour + 12) if x > 0 else '24:00'

    def plot(ax, theta, counts, formatter):
        colors = plt.cm.jet(theta / 12.0)
        ax.bar(theta, counts, width=np.pi/6, color=colors, alpha=0.5)
        ax.xaxis.set_major_formatter(tkr.FuncFormatter(formatter))

    plt.rcParams['font.size'] = 8

    bins = np.r_[0, 0.5:12, 12, 12.5:24,  23.99999]
    data = np.array(data) / (60*60)
    counts = np.histogram(data,bins)[0]

    counts[13] += counts[0]
    counts[-1] += counts[13]

    fig, axes = plt.subplots(ncols=2, figsize=(5.5, 3), dpi=200,
                             subplot_kw=dict(projection='polar'))
    fig.subplots_adjust(wspace=0.4)
    for ax in axes:
        ax.set(theta_offset=np.pi/2, theta_direction=-1,
               xticks=np.arange(0, np.pi*2, np.pi/6),
               yticks=np.arange(1, counts.max()))

    plot(axes[0], bins[1:13] * np.pi / 6, counts[1:13], hour_formatAM)
    plot(axes[1], bins[14:26] * np.pi / 6, counts[14:26], hour_formatPM)

main()

enter image description here

If we want to avoid the mis-aligned tick labels, we can set the horizontal alignment based on their position:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as tkr

def main():
    data = [ 10.49531611,  22.49511583,  10.90891806,  18.99525417,
            21.57165972,   6.687755  ,   6.52137028,  15.86534639,
            18.53823556,   6.32563583,  12.99365833,  11.06817056,
            17.29261306,  15.31288556,  19.16236667,  10.38483333,
            14.51442222,  17.01413611,   6.96102278,  15.98508611,
            16.5287    ,  15.26533889,  20.83520278,  17.21952056,
             7.3225775 ,  16.42534361,  14.38649722,  21.63573111,  16.19249444]
    data = np.array(data)*60*60
    axes = plot_clock(data)
    for ax in axes:
        realign_polar_xticks(ax)
    plt.show()

def realign_polar_xticks(ax):
    for x, label in zip(ax.get_xticks(), ax.get_xticklabels()):
        if np.sin(x) > 0.1:
            label.set_horizontalalignment('left')
        if np.sin(x) < -0.1:
            label.set_horizontalalignment('right')

def plot_clock(data):
    def hour_formatAM(x, p):
        hour = x * 6 / np.pi
        return '{:0.0f}:00'.format(hour) if x > 0 else '12:00'

    def hour_formatPM(x, p):
        hour = x * 6 / np.pi
        return '{:0.0f}:00'.format(hour + 12) if x > 0 else '24:00'

    def plot(ax, theta, counts, formatter):
        colors = plt.cm.jet(theta / 12.0)
        ax.bar(theta, counts, width=np.pi/6, color=colors, alpha=0.5)
        ax.xaxis.set_major_formatter(tkr.FuncFormatter(formatter))

    plt.rcParams['font.size'] = 8

    bins = np.r_[0, 0.5:12, 12, 12.5:24,  23.99999]
    data = np.array(data) / (60*60)
    counts = np.histogram(data,bins)[0]

    counts[13] += counts[0]
    counts[-1] += counts[13]

    fig, axes = plt.subplots(ncols=2, figsize=(5.5, 3), dpi=200,
                             subplot_kw=dict(projection='polar'))
    fig.subplots_adjust(wspace=0.5)

    for ax in axes:
        ax.set(theta_offset=np.pi/2, theta_direction=-1,
               xticks=np.arange(0, np.pi*2, np.pi/6),
               yticks=np.arange(1, counts.max()))

    plot(axes[0], bins[1:13] * np.pi / 6, counts[1:13], hour_formatAM)
    plot(axes[1], bins[14:26] * np.pi / 6, counts[14:26], hour_formatPM)
    return axes

main()

enter image description here

And finally, if you want to do this "properly", regardless of the theta direction and offset, do something like:

def realign_polar_xticks(ax):
    for theta, label in zip(ax.get_xticks(), ax.get_xticklabels()):
        theta = theta * ax.get_theta_direction() + ax.get_theta_offset()
        theta = np.pi/2 - theta
        y, x = np.cos(theta), np.sin(theta)
        if x >= 0.1:
            label.set_horizontalalignment('left')
        if x <= -0.1:
            label.set_horizontalalignment('right')
        if y >= 0.5:
            label.set_verticalalignment('bottom')
        if y <= -0.5:
            label.set_verticalalignment('top')

enter image description here

python + matplotlib: how to insert more space between the axis and the tick labels in a polar chart?

1 Answers1