numpy meshgrid 和 mgrid 的两个简单实例和解析

曾经终败给现在 2022-01-06 10:59 245阅读 0赞

[numpy.meshgrid][] 和 [numpy.mgrid][] 用于返回包含坐标向量的坐标矩阵. 当坐标矩阵为二维时, 可用于在图像变形时构建网格.

## 实例一 ##

from __future__ import print_function import numpy as np grid_y1, grid_x1 = np.meshgrid(range(5), range(3)) grid_x2, grid_y2 = np.mgrid[0:3, 0:5] # Two arrays are element-wise equal within a tolerance.
    print ("grid_x1 == grid_x2?", np.allclose(grid_x1, grid_x2))   # True. 
    print ("grid_y1 == grid_y2?", np.allclose(grid_y2, grid_y2))    # True.

注意, 对于 np.meshgrid(range(5), range(3)),

\* 返回两个数组 grid\_y1和grid\_x1，形状均为 3 x 5, 不是 5 x 3 ;   
\* 返回的第一个数组元素来自 range(5)，即 3 行，每行均为 \[0, 1, 2, 3, 4\] ;  
\* 返回的第二个数组元素来自 range(3), 即 5 列，每列均为\[0,1,2\]

## 实例二 ##

from __future__ import print_function import numpy as np grid_y1, grid_x1 = np.meshgrid(np.linspace(0,1,200), np.linspace(0,1,100))  # output 100 x 200 array
    grid_x2, grid_y2 = np.mgrid[0:1:100j, 0:1:200j]    # output 100 x 200 array # Two arrays are element-wise equal within a tolerance.
    print ("grid_x1 == grid_x2?", np.allclose(grid_x1, grid_x2))   # True. 
    print ("grid_y1 == grid_y2?", np.allclose(grid_y2, grid_y2))    # True.

注:

grid\_y1, grid\_x1 均为 100 x 200 数组.

grid\_y1 数组有 100 行, 每行均为 np.linspace(0,1,200), 与 grid\_y2 相同 ;

grid\_x1 数组有 200 列, 每列均为 np.linspace(0,1,100), 与 grid\_x2 相同 ;

0:1:100j 索引表示包含两端即 0 和 1 , 均分为 100 个点 , 与 np.linspace(0,1,100) 含义相同.

转载于:https://www.cnblogs.com/klchang/p/10633972.html

[numpy.meshgrid]: https://docs.scipy.org/doc/numpy/reference/generated/numpy.meshgrid.html
[numpy.mgrid]: https://docs.scipy.org/doc/numpy/reference/generated/numpy.mgrid.html