热图：在matplotlib中创建热图

通过matplotlib创建热图的辅助函数

> `from mlxtend.plotting import heatmap`

概述

一个简单的函数，它使用matplotlib和Viridis颜色调色板默认创建好看的热图，输入为NumPy数组。

参考文献

• -

示例 1 -- 简单热图

from mlxtend.plotting import heatmap
import matplotlib.pyplot as plt
import numpy as np
import pandas as pd

np.random.seed(123)
some_array = np.random.random((20, 30))
heatmap(some_array, figsize=(20, 10))
plt.show()

通过设置 cell_values=False 可以抑制单元格值的显示：

heatmap(some_array, figsize=(20, 10), cell_values=False)
plt.show()

示例 2 -- 作为热图的相关性矩阵

from mlxtend.plotting import heatmap
import matplotlib.pyplot as plt
import numpy as np
import pandas as pd

df = pd.read_csv('https://raw.githubusercontent.com/rasbt/'
                 'python-machine-learning-book-2nd-edition'
                 '/master/code/ch10/housing.data.txt',
                 header=None,
                 sep='\s+')

df.columns = ['CRIM', 'ZN', 'INDUS', 'CHAS', 
              'NOX', 'RM', 'AGE', 'DIS', 'RAD', 
              'TAX', 'PTRATIO', 'B', 'LSTAT', 'MEDV']
df.head()

from matplotlib import cm

cols = ['LSTAT', 'INDUS', 'NOX', 'RM', 'MEDV']

corrmat = np.corrcoef(df[cols].values.T)
fig, ax = heatmap(corrmat, column_names=cols, row_names=cols, cmap=cm.PiYG)

# 将颜色条截断设置在 -1 和 1 之间
for im in ax.get_images():
    im.set_clim(-1, 1)

plt.show()

API

heatmap(matrix, hide_spines=False, hide_ticks=False, figsize=None, cmap=None, colorbar=True, row_names=None, column_names=None, column_name_rotation=45, cell_values=True, cell_fmt='.2f', cell_font_size=None, text_color_threshold=None)

Plot a heatmap via matplotlib.

Parameters

• conf_mat : array-like, shape = [n_rows, n_columns]

  And arbitrary 2D array.

• hide_spines : bool (default: False)

  Hides axis spines if True.

• hide_ticks : bool (default: False)

  Hides axis ticks if True

• figsize : tuple (default: (2.5, 2.5))

  Height and width of the figure

• cmap : matplotlib colormap (default: None)

  Uses matplotlib.pyplot.cm.viridis if None

• colorbar : bool (default: True)

  Shows a colorbar if True

• row_names : array-like, shape = [n_rows] (default: None)

  List of row names to be used as y-axis tick labels.

• column_names : array-like, shape = [n_columns] (default: None)

  List of column names to be used as x-axis tick labels.

• column_name_rotation : int (default: 45)

  Number of degrees for rotating column x-tick labels.

• cell_values : bool (default: True)

  Plots cell values if True.

• cell_fmt : string (default: '.2f')

  Format specification for cell values (if cell_values=True)

• cell_font_size : int (default: None)

  Font size for cell values (if cell_values=True)

• text_color_threshold : float (default: None)

  Threshold for the black/white text threshold of the text annotation. Default (None) tried to infer a good threshold automatically using np.max(normed_matrix) / 2.

Returns

• fig, ax : matplotlib.pyplot subplot objects

  Figure and axis elements of the subplot.

Examples

For usage examples, please see https://rasbt.github.io/mlxtend/user_guide/plotting/heatmap/