matplotlib还提供了一个名为pylab的模块，其中包括了许多NumPy和pyplot模块中常用的函数，方便用户快速进行计算和绘图，十分适合在IPython交互式环境中使用。这里使用下面的方式载入pylab模块：

>>> import pylab as pl

1 安装numpy和matplotlib

>>> import numpy
>>> numpy.__version__

>>> import matplotlib
>>> matplotlib.__version__

 

2 两种常用图类型：Line and scatter plots(使用plot()命令), histogram(使用hist()命令)

2.1 折线图&散点图 Line and scatter plots

2.1.1 折线图 Line plots(关联一组x和y值的直线)

import numpy as np import pylab as pl   x = [1, 2, 3, 4, 5]# Make an array of x values y = [1, 4, 9, 16, 25]# Make an array of y values for each x value   pl.plot(x, y)# use pylab to plot x and y pl.show()# show the plot on the screen

 

2.1.2 散点图 Scatter plots

把pl.plot(x, y)改成pl.plot(x, y, 'o')即可，下图的蓝色版本

 

2.2  美化 Making things look pretty

2.2.1 线条颜色 Changing the line color

红色：把pl.plot(x, y, 'o')改成pl.plot(x, y, ’or’)

 

2.2.2 线条样式 Changing the line style

虚线:plot(x,y, '--')

 

2.2.3 marker样式 Changing the marker style

蓝色星型markers：plot(x,y, ’b*’)

 

2.2.4 图和轴标题以及轴坐标限度 Plot and axis titles and limits

import numpy as np import pylab as pl   x = [1, 2, 3, 4, 5]# Make an array of x values y = [1, 4, 9, 16, 25]# Make an array of y values for each x value pl.plot(x, y)# use pylab to plot x and y   pl.title(’Plot of y vs. x’)# give plot a title pl.xlabel(’x axis’)# make axis labels pl.ylabel(’y axis’)   pl.xlim(0.0, 7.0)# set axis limits pl.ylim(0.0, 30.)   pl.show()# show the plot on the screen

 

2.2.5 在一个坐标系上绘制多个图 Plotting more than one plot on the same set of axes

做法是很直接的，依次作图即可:

import numpy as np import pylab as pl   x1 = [1, 2, 3, 4, 5]# Make x, y arrays for each graph y1 = [1, 4, 9, 16, 25] x2 = [1, 2, 4, 6, 8] y2 = [2, 4, 8, 12, 16]   pl.plot(x1, y1, ’r’)# use pylab to plot x and y pl.plot(x2, y2, ’g’)   pl.title(’Plot of y vs. x’)# give plot a title pl.xlabel(’x axis’)# make axis labels pl.ylabel(’y axis’)     pl.xlim(0.0, 9.0)# set axis limits pl.ylim(0.0, 30.)     pl.show()# show the plot on the screen

 

2.2.6  图例 Figure legends

pl.legend((plot1, plot2), (’label1, label2’), 'best’, numpoints=1)

其中第三个参数表示图例放置的位置:'best’‘upper right’, ‘upper left’, ‘center’, ‘lower left’, ‘lower right’.

如果在当前figure里plot的时候已经指定了label，如plt.plot(x,z,label="$cos(x^2)$")，直接调用plt.legend()就可以了哦。

import numpy as np import pylab as pl   x1 = [1, 2, 3, 4, 5]# Make x, y arrays for each graph y1 = [1, 4, 9, 16, 25] x2 = [1, 2, 4, 6, 8] y2 = [2, 4, 8, 12, 16]   plot1 = pl.plot(x1, y1, ’r’)# use pylab to plot x and y : Give your plots names plot2 = pl.plot(x2, y2, ’go’)   pl.title(’Plot of y vs. x’)# give plot a title pl.xlabel(’x axis’)# make axis labels pl.ylabel(’y axis’)     pl.xlim(0.0, 9.0)# set axis limits pl.ylim(0.0, 30.)     pl.legend([plot1, plot2], (’red line’, ’green circles’), ’best’, numpoints=1)# make legend pl.show()# show the plot on the screen