numpy meshgrid() 将向量拉伸为二维矩阵

np.meshgrid()
np.meshgrid从坐标向量返回坐标矩阵。

将两个向量拉成一个矩阵数组：

meshgrid.png

In [18]: x = np.array([0,1,2])
In [19]: y = np.array([4,5,6,7])
In [20]: xs,ys = np.meshgrid(x,y)

In [21]: xs
Out[21]:
array([[0, 1, 2],
       [0, 1, 2],
       [0, 1, 2],
       [0, 1, 2]])

In [22]: ys
Out[22]:
array([[4, 4, 4],
       [5, 5, 5],
       [6, 6, 6],
       [7, 7, 7]])

2. 画一个灰度图，这个十分好玩

#uses Ipython
In [24]: points = np.arange(-5,5,0.01)
In [25]: xs,ys = np.meshgrid(points,points)
In [26]: import matplotlib.pyplot as plt
In [33]: a = xs ** 2 + ys ** 2
In [35]: plt.imshow(np.sqrt(a),cmap = plt.cm.gray);plt.colorbar();plt.show()

grey-degree.png

参考资料：

1. numpy之meshgrid和where
2. 《利用python进行数据分析》

2018.5.23