Matplotlib - 绘图基础

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这篇随笔主要介绍利用 Matplotlib 绘制图像，包括 figure 和 subplot 的创建，刻度、标签和图例的设置、标题和轴标签的设置以及添加文本、添加图形等功能

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import matplotlib.pyplot as plt
import numpy as np
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%matplotlib inline

plt.plot( data, color, linestyle, marker, label, drawstyle )

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data = np.arange(10)
plt.plot(data)
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[<matplotlib.lines.Line2D at 0x11dba8e1e50>]

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color, linestyle, marker, label : 颜色, 标记, 线型, 图例

plt.subplots( nrows, ncols, sharex, sharey ) : 调整图片大小

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data = np.random.randn(30).cumsum()
plt.plot(data, color='b', linestyle='--', marker='o')
plt.plot(-data, 'ro--')
plt.subplots_adjust(top=0.6)

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drawstyle

plt.legend( loc ) : 设置图例

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data = np.random.randn(30).cumsum()
plt.plot(data, 'k--', label='Default')
plt.plot(data, 'k-', drawstyle='steps-post', label='steps-post')
plt.legend(loc='best')
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<matplotlib.legend.Legend at 0x11dbb0d9850>

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Figure 和 Subplot

plt.figure( figsize ) : 创建一个的 Figure 对象; matplotlib 的图像都位于 Figure 对象中

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fig = plt.figure() #创建一个的 Figure 对象
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<Figure size 432x288 with 0 Axes>

fig.add_subplot( nrows, ncols, index ) : 创建一个的 AxesSubplot 对象, 位于 [ nrows, ncols ] 的 index 位置

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fig = plt.figure() #创建一个的 Figure 对象
ax1 = fig.add_subplot(2, 2, 1)
ax2 = fig.add_subplot(2, 2, 2)
ax3 = fig.add_subplot(2, 2, 3)
ax4 = fig.add_subplot(2, 2, 4)
data = np.random.randn(100)
plt.plot(data.cumsum(), 'k--')
ax1.plot(data.cumsum())
ax2.hist(data, bins=12, color='k', alpha=0.3) # 统计直方图
ax3.scatter(np.arange(100), data.cumsum()) # 散点图
plt.savefig('normal.png', dpi=1080, bbox_inches='tight')

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plt.subplots( nrows, ncols, sharex, sharey ) : 创建 Figure 对象和 一组 AxesSubplot 对象（存放于 ndarray 中）

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fig, axes = plt.subplots(2, 1, sharex='all', sharey='all') # 共享x轴, y轴
# fig : Figure 对象 ; axes : ndarray 对象, 用于索引 AxesSubplot
plt.plot(data, 'k--')
axes[0].plot(data) #对图片进行索引
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[<matplotlib.lines.Line2D at 0x11dbb291610>]

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plt.subplots_adjust( left, bottom, right, top, wspace, hspace ) : 调整 subplot 大小和间距

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fig, axes = plt.subplots(2, 2, sharex=True, sharey=True)
for i in range(2):
    for j in range(2):
        axes[i, j].hist(np.random.randn(500), bins=50, color='k' ,alpha=0.5)
plt.subplots_adjust(left=0, bottom=0, right=2, top=1.2, 
                    wspace=0, hspace=0)

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刻度, 标签 和 图例

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data = np.random.randn(500)
_ = plt.hist(data, bins=50, color='k' ,alpha=0.5)

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plt.xlim( ), plt.xlim( [ start, stop] ) : 控制绘图范围

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plt.hist(data, bins=50, color='k' ,alpha=0.5)
plt.xlim(), plt.xlim([-2, 2])
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((-3.411006317547548, 3.221768778645931), (-2.0, 2.0))

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ax.get_xlim( ), ax.set_xlim( [ start, stop] ) : 控制绘图范围

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5)
ax.get_xlim(), ax.set_xlim([-2,2])
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((-3.411006317547548, 3.221768778645931), (-2.0, 2.0))

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plt.xticks( ), plt.xticks( ticks, labels ) : 控制刻度位置和标签

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data = np.random.randn(500)
plt.hist(data, bins=50, color='k' ,alpha=0.5)
plt.xticks(ticks = [-2, 0, 2] )
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([<matplotlib.axis.XTick at 0x11dbb949430>,
  <matplotlib.axis.XTick at 0x11dbb949400>,
  <matplotlib.axis.XTick at 0x11dbb937f40>],
 [Text(0, 0, ''), Text(0, 0, ''), Text(0, 0, '')])

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data = np.random.randn(500)
plt.hist(data, bins=50, color='k' ,alpha=0.5)
plt.xticks(ticks = [-2, 0, 2], labels=['negative', 'zero', 'positive'] )
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([<matplotlib.axis.XTick at 0x11dbba06310>,
  <matplotlib.axis.XTick at 0x11dbba062e0>,
  <matplotlib.axis.XTick at 0x11dbb8735e0>],
 [Text(-2, 0, 'negative'), Text(0, 0, 'zero'), Text(2, 0, 'positive')])

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ax.get_xticks( ), ax.set_xticks( ticks ) : 控制刻度位置

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5)
ax.get_xticks(), ax.set_xticks([-2, 0, 2])
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(array([-4., -3., -2., -1.,  0.,  1.,  2.,  3.,  4.]),
 [<matplotlib.axis.XTick at 0x11dbbac5760>,
  <matplotlib.axis.XTick at 0x11dbbac5730>,
  <matplotlib.axis.XTick at 0x11dbbabe040>])

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ax.get_xticklabels( ), ax.set_xticklabels( list ) : 控制刻度标签

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5)
ax.set_xticks([-2, 0, 2])
ax.set_xticklabels(['negative', 'zero', 'positive'])
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[Text(-2, 0, 'negative'), Text(0, 0, 'zero'), Text(2, 0, 'positive')]

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标题 和 轴标签

ax.set_xlabel( xlabel ), ax.set_title( title )

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5)
ax.set_xlabel('XLABEL'), ax.set_title('TITLE')
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(Text(0.5, 0, 'XLABEL'), Text(0.5, 1.0, 'TITLE'))

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ax.set( *kwargs )*

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5)
props = {
    'title': 'My first matplotlib plot',
    'xlabel': 'Stages'
}
ax.set(**props)
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[Text(0.5, 1.0, 'My first matplotlib plot'), Text(0.5, 0, 'Stages')]

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图例

ax.legend( loc )

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5, label='one')
ax.legend(loc='best')
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<matplotlib.legend.Legend at 0x11dbcdba2e0>

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添加文本

ax.text( x, y, str, rotation, ha, va, fontdict = dict( ... ), bbox = dict( ... ) )

fontdict = dict( fontsize, color, family, weight )
bbox = dict( facecolor, edgecolor, edgewidth, alpha, pad )

rotation : 旋转 , ha : 左右对齐方式 , va : 上下对齐方式

fontdict : 字体属性字典
family : 字体 , weight : 磅值

bbox : 边框填充属性字典
facecolor : 填充色 , edgecolor : 边框色, edgewidth : 边框粗细
alpha : 透明度 , pad : 文本与框周围距离, boxstyle : 形状参数

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5, label='one')
ax.text(0, 10, 'Hello world!', ha = 'center', va = 'bottom', 
        fontdict = dict(family='monospace', fontsize=20), 
        bbox = dict(facecolor='#74c476', edgecolor='b', alpha=0.7))
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Text(0, 10, 'Hello world!')

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ax.annotate( text, xy, xytext, xycoords, textcoords, ha, va, weight, color, bbox, arrowprops )

xy = ( x, y )
xytext = ( x, y )
bbox = dict( facecolor, edgecolor, edgewidth, alpha, pad )
arrowprops = dict( facecolor, hatch, alpha, shrink, width, headwidth, headlength )

xy : 箭头指向位置 , xytext : 文本位置
xycoords : 箭头位置的参考坐标系 , textcoords : 选择文本位置的参考坐标系
ha : 文本左右对齐方式 , va : 文本上下对齐方式
weight : 文本磅值 , va : 文本颜色
bbox : 文本边框填充属性字典

arrowprops : 箭头属性字典
facecolor : 填充色 , hatch : 填充形状
shrink : 两端收缩控制, width : 箭身宽度
headwidth : 箭头宽度, headlength : 箭头长度

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fig, ax = plt.subplots(1, 1)
ax.hist(data, bins=50, color='k' ,alpha=0.5, label='one')
ax.annotate('Hello World!', (0, 10), (2, 25), ha = 'center', va = 'top', fontsize=20, 
            arrowprops=dict(facecolor='k', width=0.1, headwidth=5, headlength=5, shrink=0.05), 
            bbox = dict(facecolor='#74c476', edgecolor='b', alpha=0.7)
            )
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Text(2, 25, 'Hello World!')

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添加图形

ax.add_patch( shp )

plt.Rectangle( xy, width, height, angle, color, alpha )
plt.Circle( xy, r, color, alpha )
plt.Polygon( [ xy1, xy2, ... ], color, alpha )

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fig = plt.figure(figsize=(4.5, 9.5))
ax = fig.add_subplot(1, 1, 1)
ax.set_xlim(0,9)
ax.set_ylim(1,20)
# 正方形
rect = plt.Rectangle((0, 1), 9, 20, color='#b7e464', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((0.6, 13.9), 3.2, 5.5, color='#8db53c', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((0.7, 14), 3, 5.3, color='#b7e464', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((6.3, 0), 2, 20, color='k', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((5.5, 0), 0.4, 20, color='k', alpha=1)
ax.add_patch(rect)
# 圆形
circ = plt.Circle((1.75, 15.15), 0.8, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((1.75, 15.15), 0.25, color='#121233', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((1.75, 18.15), 0.8, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((1.75, 18.15), 0.25, color='#121233', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 16.65), 0.4, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 16.65), 0.25, color='#121233', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 15.15), 0.35, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 18.15), 0.35, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 15.15), 0.25, color='w', alpha=0.9)
ax.add_patch(circ)
circ = plt.Circle((3.1, 18.15), 0.25, color='w', alpha=0.9)
ax.add_patch(circ)
ax.text(7.3, 2.5, 'realme', ha = 'center', va = 'bottom', rotation=90, 
        fontdict = dict(fontsize=30, color='#74c476'))
for i in range(0, 9):
        ax.text(5.7, 1.4+i*2, 'DARE TO LEAP', ha = 'center', va = 'bottom', rotation=90, 
        fontdict = dict(fontsize=7, color='w'))
ax.text(5.7, 1.4+(i+1)*2, 'DAR', ha = 'center', va = 'bottom', rotation=90, 
        fontdict = dict(fontsize=7, color='w'))
ax.text(1.75, 16.75, '64MP', ha = 'center', va = 'center', alpha=0.9, 
        fontdict = dict(fontsize=16, color='#EEEEEE', weight='light'))
ax.text(1.75, 16.35, 'MATRIX CAMERA', ha = 'center', va = 'center', alpha=0.9, 
        fontdict = dict(fontsize=5, color='#EEEEEE', weight='light'))
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Text(1.75, 16.35, 'MATRIX CAMERA')

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fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
pgon = plt.Polygon([[0.1, 0.1], [0.6, 0.9], [0.9, 0.6]])
ax.add_patch(pgon)
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<matplotlib.patches.Polygon at 0x11dbb80d640>

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保存图片

plt.savefig( fname, dpi, bbox_inches )

dpi : 每英寸点数分辨率, default: 100
bbox_inches : 控制图片周围白边, bbox_inches = 'tight'

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fig = plt.figure(figsize=(4.5, 9.5))
ax = fig.add_subplot(1, 1, 1)
ax.set_xlim(0,9)
ax.set_ylim(1,20)
# 正方形
rect = plt.Rectangle((0, 1), 9, 20, color='#b7e464', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((0.6, 13.9), 3.2, 5.5, color='#8db53c', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((0.7, 14), 3, 5.3, color='#b7e464', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((6.3, 0), 2, 20, color='k', alpha=1)
ax.add_patch(rect)
rect = plt.Rectangle((5.5, 0), 0.4, 20, color='k', alpha=1)
ax.add_patch(rect)
# 圆形
circ = plt.Circle((1.75, 15.15), 0.8, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((1.75, 15.15), 0.25, color='#121233', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((1.75, 18.15), 0.8, color='k', alpha=1)
ax.add_patch(circ)## 
circ = plt.Circle((1.75, 18.15), 0.25, color='#121233', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 16.65), 0.4, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 16.65), 0.25, color='#121233', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 15.15), 0.35, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 18.15), 0.35, color='k', alpha=1)
ax.add_patch(circ)
circ = plt.Circle((3.1, 15.15), 0.25, color='w', alpha=0.9)
ax.add_patch(circ)
circ = plt.Circle((3.1, 18.15), 0.25, color='w', alpha=0.9)
ax.add_patch(circ)
ax.text(7.3, 2.5, 'realme', ha = 'center', va = 'bottom', rotation=90, 
        fontdict = dict(fontsize=30, color='#74c476'))
for i in range(0, 9):
        ax.text(5.7, 1.4+i*2, 'DARE TO LEAP', ha = 'center', va = 'bottom', rotation=90, 
        fontdict = dict(fontsize=7, color='w'))
ax.text(5.7, 1.4+(i+1)*2, 'DAR', ha = 'center', va = 'bottom', rotation=90, 
        fontdict = dict(fontsize=7, color='w'))
ax.text(1.75, 16.75, '64MP', ha = 'center', va = 'center', alpha=0.9, 
        fontdict = dict(fontsize=16, color='#EEEEEE', weight='light'))
ax.text(1.75, 16.35, 'MATRIX CAMERA', ha = 'center', va = 'center', alpha=0.9, 
        fontdict = dict(fontsize=5, color='#EEEEEE', weight='light'))
plt.savefig('realmeneo2.png', dpi=1080, bbox_inches='tight')

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matplotlib 的全局配置

plt.rc( group, **kwargs ) : 全局参数的定义

group : figure, font, axes, xtick, grid, legend , 希望定义的对象

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# plt.rc('figure', figsize=(4, 3))
# font_options = {
#     'family' : 'monospace', 
#     'weight' : 'bold', 
#     'size' : 10}
# plt.rc('font', **font_options)
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fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.text(0.2, 0.2, 'Hello world!', ha = 'left', va = 'bottom', 
        fontdict=dict(fontsize=20),   
        bbox = dict(facecolor='#74c476', edgecolor='b', alpha=0.7))
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Text(0.2, 0.2, 'Hello world!')

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