Python: ndarray operation

最新推荐文章于 2025-08-07 15:08:44 发布

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最新推荐文章于 2025-08-07 15:08:44 发布

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文章标签： python

原文链接：http://www.cnblogs.com/docnan/p/7157788.html

本文介绍了Python中NumPy库的核心数据类型ndarray的高效使用方法，包括如何快速读取矩阵的部分索引、如何对ndarray进行翻转操作及错误处理，并展示了两个ndarray合并的具体方式。

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Ndarray is most used data type in python, because many modules such as pylab, numpy use ndarray as default data type to undertake matrix operation. So using ndarray type of data will quickly accelerate the speed of python calculation.

Read part of indices from an ndarray matrix
Suppose we have a matrix in ndarray type as M: 10*20, X:10, if we just wish to get the first dimension of this matrix we can set the code like this:
M[0:3,:].shape=(3,20)
X[0:3].shape=(3)
The index begin with 0 end with 2, the last index 3 is not included!
reorder ndarray matrix
x=numpy.array([0,1,2,3])
y=numpy.array([[0,1,2,3],[0,2,4,6]])
xf=numpy.fliplr(x)
error Input must be >=2-d, this error might suggest that function fliplr can only work on matrix whose dimension bigger or equal than 2
yf=array([][3,2,1,0],[6,4,2,0])
combine two ndarray
A=numpy.concatenate([A1,A2])

转载于:https://www.cnblogs.com/docnan/p/7157788.html