matplotlib的表格图例布局

Question

我有一个9行的图,表示具有两个不同参数的数据集,比如f_11,f_12,f_13,...,f_33.为了使图(有点)更清晰,我将第一个参数编码为线的颜色,第二个参数编码为线型(因此f_11为红色和虚线,f12为红色和虚线,f21为绿色和虚线,f22为绿色和点缀等).所以,对于传说,我想做一个3x3的桌子,看起来像

       | value1 | value2 | value3
---------------------------------
value1 |
value2 |    <artists go there>
value3 |

有什么办法可以用matplotlib来做这个吗？一个想法是用LaTeX制作这个盒子,但是我需要一种方法来将传奇艺术家绘制在正确的位置.

谢谢!

(来自matplotlib-users的crosspossted)

Answer 1

这不是一个很容易的问题,但我想出来了.我使用的技巧是初始化一个充当句柄的空矩形.这些额外的空句柄用于构造表.我使用handletextpad以下方法摆脱了过多的空间:

import numpy
import pylab
import matplotlib.pyplot as plt
from matplotlib.patches import Rectangle

fig = plt.figure()
ax = fig.add_subplot(111)

im1 ,= ax.plot(range(10), pylab.randn(10), "r--")
im2 ,= ax.plot(range(10), pylab.randn(10), "g--")
im3 ,= ax.plot(range(10), pylab.randn(10), "b--")
im4 ,= ax.plot(range(10), pylab.randn(10), "r.")
im5 ,= ax.plot(range(10), pylab.randn(10), "g.")
im6 ,= ax.plot(range(10), pylab.randn(10), "b.")
im7 ,= ax.plot(range(10), pylab.randn(10), "r^")
im8 ,= ax.plot(range(10), pylab.randn(10), "g^")
im9 ,= ax.plot(range(10), pylab.randn(10), "b^")

# create blank rectangle
extra = Rectangle((0, 0), 1, 1, fc="w", fill=False, edgecolor='none', linewidth=0)

#Create organized list containing all handles for table. Extra represent empty space
legend_handle = [extra, extra, extra, extra, extra, im1, im2, im3, extra, im4, im5, im6, extra, im7, im8, im9]

#Define the labels
label_row_1 = [r"$f_{i,j}$", r"$i = 1$", r"$i = 2$", r"$i = 3$"]
label_j_1 = [r"$j = 1$"]
label_j_2 = [r"$j = 2$"]
label_j_3 = [r"$j = 3$"]
label_empty = [""]

#organize labels for table construction
legend_labels = numpy.concatenate([label_row_1, label_j_1, label_empty * 3, label_j_2, label_empty * 3, label_j_3, label_empty * 3])

#Create legend
ax.legend(legend_handle, legend_labels, 
          loc = 9, ncol = 4, shadow = True, handletextpad = -2)

plt.show()

Answer 2

扩大对花花公子的答案，我试图把它变成一个复制粘贴的解决方案通过创建一个功能（见/复制下文），可以自动表传奇的产生，这样你只需要以下，而不是添加ax.legend()到你的情节：

tablelegend(ax, ncol=3, bbox_to_anchor=(1, 1), 
            row_labels=['$i=2$', '$i=3$'], 
            col_labels=['$j=1$', '$j=2$', '$j=3$'], 
            title_label='$f_{i,j}$')

row_labels,col_labels和title_label都是可选的，例如，您可以创建一个带有列标题但没有行标题的图例表。

完整示例用法

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = plt.gca()

ax.plot(range(10), np.random.randn(10), "r:", label='$i=1$, $j=1$')
ax.plot(range(10), np.random.randn(10), "g:", label='$i=2$, $j=1$')
ax.plot(range(10), np.random.randn(10), "b:", label='$i=3$, $j=1$')
ax.plot(range(10), np.random.randn(10), "r.", label='$i=1$, $j=2$')
ax.plot(range(10), np.random.randn(10), "g.", label='$i=2$, $j=2$')
ax.plot(range(10), np.random.randn(10), "b.", label='$i=3$, $j=2$')
ax.plot(range(10), np.random.randn(10), "r^", label='$i=1$, $j=3$')
ax.plot(range(10), np.random.randn(10), "g^", label='$i=2$, $j=3$')
ax.plot(range(10), np.random.randn(10), "b^", label='$i=3$, $j=3$')

tablelegend(ax, ncol=3, bbox_to_anchor=(1, 1), 
            row_labels=['$i=1$', '$i=2$', '$i=3$'], 
            col_labels=['$j=1$', '$j=2$', '$j=3$'], 
            title_label='$f_{i,j}$')

该tablelegend功能

import matplotlib.legend as mlegend
from matplotlib.patches import Rectangle

def tablelegend(ax, col_labels=None, row_labels=None, title_label="", *args, **kwargs):
    """
    Place a table legend on the axes.
    
    Creates a legend where the labels are not directly placed with the artists, 
    but are used as row and column headers, looking like this:
    
    title_label   | col_labels[1] | col_labels[2] | col_labels[3]
    -------------------------------------------------------------
    row_labels[1] |
    row_labels[2] |              <artists go there>
    row_labels[3] |
    
    
    Parameters
    ----------
    
    ax : `matplotlib.axes.Axes`
        The artist that contains the legend table, i.e. current axes instant.
        
    col_labels : list of str, optional
        A list of labels to be used as column headers in the legend table.
        `len(col_labels)` needs to match `ncol`.
        
    row_labels : list of str, optional
        A list of labels to be used as row headers in the legend table.
        `len(row_labels)` needs to match `len(handles) // ncol`.
        
    title_label : str, optional
        Label for the top left corner in the legend table.
        
    ncol : int
        Number of columns.
        

    Other Parameters
    ----------------
    
    Refer to `matplotlib.legend.Legend` for other parameters.
    
    """
    #################### same as `matplotlib.axes.Axes.legend` #####################
    handles, labels, extra_args, kwargs = mlegend._parse_legend_args([ax], *args, **kwargs)
    if len(extra_args):
        raise TypeError('legend only accepts two non-keyword arguments')
    
    if col_labels is None and row_labels is None:
        ax.legend_ = mlegend.Legend(ax, handles, labels, **kwargs)
        ax.legend_._remove_method = ax._remove_legend
        return ax.legend_
    #################### modifications for table legend ############################
    else:
        ncol = kwargs.pop('ncol')
        handletextpad = kwargs.pop('handletextpad', 0 if col_labels is None else -2)
        title_label = [title_label]
        
        # blank rectangle handle
        extra = [Rectangle((0, 0), 1, 1, fc="w", fill=False, edgecolor='none', linewidth=0)]
        
        # empty label
        empty = [""]
        
        # number of rows infered from number of handles and desired number of columns
        nrow = len(handles) // ncol
        
        # organise the list of handles and labels for table construction
        if col_labels is None:
            assert nrow == len(row_labels), "nrow = len(handles) // ncol = %s, but should be equal to len(row_labels) = %s." % (nrow, len(row_labels))
            leg_handles = extra * nrow
            leg_labels  = row_labels
        elif row_labels is None:
            assert ncol == len(col_labels), "ncol = %s, but should be equal to len(col_labels) = %s." % (ncol, len(col_labels))
            leg_handles = []
            leg_labels  = []
        else:
            assert nrow == len(row_labels), "nrow = len(handles) // ncol = %s, but should be equal to len(row_labels) = %s." % (nrow, len(row_labels))
            assert ncol == len(col_labels), "ncol = %s, but should be equal to len(col_labels) = %s." % (ncol, len(col_labels))
            leg_handles = extra + extra * nrow
            leg_labels  = title_label + row_labels
        for col in range(ncol):
            if col_labels is not None:
                leg_handles += extra
                leg_labels  += [col_labels[col]]
            leg_handles += handles[col*nrow:(col+1)*nrow]
            leg_labels  += empty * nrow
        
        # Create legend
        ax.legend_ = mlegend.Legend(ax, leg_handles, leg_labels, ncol=ncol+int(row_labels is not None), handletextpad=handletextpad, **kwargs)
        ax.legend_._remove_method = ax._remove_legend
        return ax.legend_