matplotlib是python的一個開源的2D繪相簿，它的原作者是John D. Hunter，因為在設計上借鑑了matlab，所以成為matplotlib。和Pillow一樣是被廣泛使用的繪圖功能，而在深度學習相關的部分，matplotlib得寵的多。這篇文章將簡單介紹一下如何安裝以及使用它來畫一些非常常見的統計圖形。

概要資訊

專案	說明
官方網站	http://matplotlib.org
開源/閉源	開源
License類別	BSD License
程式碼管理地址	https://github.com/matplotlib/matplotlib
開發語言	Python
當前穩定版本	2.2.2LTS （python2）
更新頻度	平均每季度數次

注意事項：由於Python2支援到2020年，很多python庫都開始主要支援python3了，matplotlib的主分支也已經是python3了。而這篇文章中為了簡單，安裝和demo程式碼依然是在python2.7上進行驗證的。

安裝

使用pip install即可直接安裝。安裝日誌如下：

liumiaocn:tmp liumiao$ python -mpip install -U pip
Requirement already up-to-date: pip in /usr/local/lib/python2.7/site-packages (10.0.1)
liumiaocn:tmp liumiao$ 
liumiaocn:tmp liumiao$ python -mpip install -U matplotlib
Collecting matplotlib
  Downloading https://files.pythonhosted.org/packages/61/38/d70e8bf77d5cb27d5f3595edd0b3978825063feadd023786d2591e393e6e/matplotlib-2.2.2-cp27-cp27m-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl (13.7MB)
    100% |████████████████████████████████| 13.7MB 2.1MB/s 
Collecting pyparsing!=2.0.4,!=2.1.2,!=2.1.6,>=2.0.1 (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/6a/8a/718fd7d3458f9fab8e67186b00abdd345b639976bc7fb3ae722e1b026a50/pyparsing-2.2.0-py2.py3-none-any.whl (56kB)
    100% |████████████████████████████████| 61kB 5.8MB/s 
Collecting backports.functools-lru-cache (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/03/8e/2424c0e65c4a066e28f539364deee49b6451f8fcd4f718fefa50cc3dcf48/backports.functools_lru_cache-1.5-py2.py3-none-any.whl
Collecting subprocess32 (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/fa/60/b50459f291cae6bc1d0ff711b75e5130684fd3949370fdba78f6c57c1903/subprocess32-3.5.2-cp27-cp27m-macosx_10_6_intel.whl
Collecting pytz (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/dc/83/15f7833b70d3e067ca91467ca245bae0f6fe56ddc7451aa0dc5606b120f2/pytz-2018.4-py2.py3-none-any.whl (510kB)
    100% |████████████████████████████████| 512kB 8.9MB/s 
Requirement not upgraded as not directly required: six>=1.10 in /usr/local/lib/python2.7/site-packages (from matplotlib) (1.11.0)
Collecting python-dateutil>=2.1 (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/cf/f5/af2b09c957ace60dcfac112b669c45c8c97e32f94aa8b56da4c6d1682825/python_dateutil-2.7.3-py2.py3-none-any.whl (211kB)
    100% |████████████████████████████████| 215kB 7.2MB/s 
Collecting kiwisolver>=1.0.1 (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/79/d8/94633718f3f77dcb638687a77ba199325a1cb158d2d4b00c9dc17f2b5c72/kiwisolver-1.0.1-cp27-cp27m-macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64.macosx_10_10_intel.macosx_10_10_x86_64.whl (110kB)
    100% |████████████████████████████████| 112kB 5.9MB/s 
Collecting cycler>=0.10 (from matplotlib)
  Downloading https://files.pythonhosted.org/packages/f7/d2/e07d3ebb2bd7af696440ce7e754c59dd546ffe1bbe732c8ab68b9c834e61/cycler-0.10.0-py2.py3-none-any.whl
Requirement not upgraded as not directly required: numpy>=1.7.1 in /usr/local/lib/python2.7/site-packages (from matplotlib) (1.14.5)
Requirement not upgraded as not directly required: setuptools in /usr/local/lib/python2.7/site-packages (from kiwisolver>=1.0.1->matplotlib) (39.2.0)
Installing collected packages: pyparsing, backports.functools-lru-cache, subprocess32, pytz, python-dateutil, kiwisolver, cycler, matplotlib
Successfully installed backports.functools-lru-cache-1.5 cycler-0.10.0 kiwisolver-1.0.1 matplotlib-2.2.2 pyparsing-2.2.0 python-dateutil-2.7.3 pytz-2018.4 subprocess32-3.5.2
liumiaocn:tmp liumiao$

確認

liumiaocn:~ liumiao$ pip show matplotlib
Name: matplotlib
Version: 2.2.2
Summary: Python plotting package
Home-page: http://matplotlib.org
Author: John D. Hunter, Michael Droettboom
Author-email: matplotlib-users@python.org
License: BSD
Location: /usr/local/lib/python2.7/site-packages
Requires: pyparsing, backports.functools-lru-cache, subprocess32, pytz, six, python-dateutil, kiwisolver, cycler, numpy
Required-by: 
liumiaocn:~ liumiao$

使用

正弦函式

我們使用numpy和matplotlib可以非常簡單地就能夠畫出正弦的波形圖，具體程式碼如下：

liumiaocn:plot liumiao$ cat plot-1.py 
#!/usr/local/bin/python

import numpy as np
import matplotlib.pyplot as plot

print("y=sin(x): x with range fo -4pi to 4pi")
x=np.arange(-4*np.pi, 4*np.pi, 0.1)
y=np.sin(x)

#print sin
plot.plot(x,y)
plot.show()
liumiaocn:plot liumiao$

執行&結果確認

liumiaocn:plot liumiao$ python plot-1.py 
y=sin(x): x with range fo -4pi to 4pi

直方圖

最簡單的直方圖的做法，可以通過bar或者hist來建立

liumiaocn:plot liumiao$ cat plot-2.py 
import numpy as np
import matplotlib.pyplot as plt

x = np.arange(7)
y = (10,15,24,7,14,30,20)

plt.bar(x,y)
plt.show()
liumiaocn:plot liumiao$

餅圖

使用pie函式建立餅圖

liumiaocn:plot liumiao$ cat plot-3.py 
#!/usr/local/bin/python

import matplotlib.pyplot as plt

dateinf = '06/01', '06/02', '06/03', '06/04', '06/05', '06/06', '06/07'
bugnums = [11,22,7,29,24,15,18]

plt.pie(bugnums, labels=dateinf)
plt.show()
liumiaocn:plot liumiao$