Adding Legend To A Radarchart In Python

I want to create a radarchart with legends for every plot that is created but until now it has been impossible. Then, you can see the code used to create the plot (thanks to anothe

Solution 1:

In case someone is interested, the code of the ComplexRadar comes from here. The ComplexRadar class uses many axes and makes all of them invisible, so the best way to create a legend here, would be to create a new axes to put the legend in. For that we need the handles of the plotted lines, so we need to change the ComplexRadar.plot() method to return the line. We then need to collect those lines in a list (call it lax) and supply them to the new legend.

I did make some changes to the code to make it work in python 2.7 and also to make it more comprehensible to myself. Here is, what should work:

import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns 
import pandas as pd

def_scale_data(data, ranges):
    """scales data[1:] to ranges[0],
    """for d, (y1, y2) inzip(data[1:], ranges[1:]):
        assert (y1 <= d <= y2) or (y2 <= d <= y1)
    x1, x2 = ranges[0]
    d = data[0]
    sdata = [d]
    for d, (y1, y2) inzip(data[1:], ranges[1:]):
        sdata.append((d-y1) / (y2-y1) 
                     * (x2 - x1) + x1)
    return sdata

classComplexRadar():
    def__init__(self, fig, variables, ranges,
                 n_ordinate_levels=6):
        angles = np.arange(0, 360, 360./len(variables))

        axes = [fig.add_axes([0.1,0.1,0.9,0.9],polar=True,
                label = "axes{}".format(i)) 
                for i inrange(len(variables))]
        l, text = axes[0].set_thetagrids(angles, 
                                         labels=variables)
        [txt.set_rotation(angle-90) for txt, angle 
             inzip(text, angles)]
        for ax in axes[1:]:
            ax.patch.set_visible(False)
            ax.grid("off")
            ax.xaxis.set_visible(False)
        for i, ax inenumerate(axes):
            grid = np.linspace(*ranges[i], 
                               num=n_ordinate_levels)
            gridlabel = ["{}".format(round(x,2)) 
                         for x in grid]
            if ranges[i][0] > ranges[i][1]:
                grid = grid[::-1] # hack to invert grid# gridlabels aren't reversed
            gridlabel[0] = ""# clean up origin
            ax.set_rgrids(grid, labels=gridlabel,
                         angle=angles[i])
            #ax.spines["polar"].set_visible(False)
            ax.set_ylim(*ranges[i])
        # variables for plotting
        self.angle = np.deg2rad(np.r_[angles, angles[0]])
        self.ranges = ranges
        self.ax = axes[0]

    defplot(self, data, *args, **kw):
        sdata = _scale_data(data, self.ranges)
        l = self.ax.plot(self.angle, np.r_[sdata, sdata[0]], *args, **kw)
        return l

    deffill(self, data, *args, **kw):
        sdata = _scale_data(data, self.ranges)
        self.ax.fill(self.angle, np.r_[sdata, sdata[0]], *args, **kw)



index = ["Carl","Michael","Peter","Louis","Sarah", "Laura","Nicholas"]      
df = pd.DataFrame({
    "Spe": pd.Series([89, 83, 70, 60, 30, 49, 28]),
    "Str": pd.Series([69, 53, 30, 20, 10, 29, 48]),
    "Det": pd.Series([82, 44, 79, 39, 20, 10, 85]),
    "Extr": pd.Series([59, 74, 29, 36, 18, 29, 18]),
    "Int": pd.Series([63, 11, 20, 36, 97, 58, 91]),
    "Est": pd.Series([12, 69, 89, 59, 19, 58, 98]),
    "Ape": pd.Series([29, 13, 94, 30, 20, 10, 67]),
})

variables = [k[0] for k in df.iteritems()]

ranges = [(1.,100.),(1.,100.),(1.,100.),(1.,100.),(1.,100.),(1.,100.),(1.,100.)] 
fig1 = plt.figure(figsize=(8, 8))
radar = ComplexRadar(fig1, variables, ranges)
lax = []
for i, name  inenumerate(index):
    data=df.iloc[i].values
    l, = radar.plot(data, label=name)
    lax.append(l)
    radar.fill(data,alpha=0.2)

legendax = fig1.add_axes([0.8,0.8,0.1,.1])
legendax.legend(handles = lax, labels=index, loc=3, bbox_to_anchor=(0,0,1,1), bbox_transform=fig1.transFigure )

legendax.axis('off')
sns.plt.show()

producing the following plot