In everyday data processing for Machine Learning and Data Science projects, we encounter unique situations, those require boilerplate code to solve the problem. Over the period some of those are converted into base features provided by the core langu…

numpy.argpartition(a, kth, axis=-1, kind='introselect', order=None) 在快排算法中,有一个典型的操作:partition.这个操作指:根据一个数值x,把数组中的元素划分成两半,使得index前面的元素都不大于x,index后面的元素都不小于x. numpy中的argpartition()函数就是起的这个作用.对于传入的数组a,先用O(n)复杂度求出第k大的数字,然后利用这个第k大的数字将数组a划分成两半. 此函数不对原数组进行操作…

1. 两者的区别在于返回拷贝(copy)还是返回视图(view),numpy.flatten()返回一份拷贝,对拷贝所做的修改不会影响(reflects)原始矩阵,而numpy.ravel()返回的是视图(view,也颇有几分C/C++引用reference的意味),会影响(reflects)原始矩阵.相当于reshape(-1) 或者 reshape(np.array.size)…

a = np.arange(2*4*4) b = a.reshape(1,4,4,2)           #应该这样按反序来理解:最后一个2是一个只有2个元素的向量,最后的4,2代表4×2的矩阵,最后的4×4×2代表立体张量,第一个1代表只有一个这样的张量(即该张量在第四维度只有一个元素). c = a.reshape(2,4,4,1)        #应该这样按反序来理解:最后一个1是只有一个1个元素的向量,最后的4,1代表4×1的矩阵(可降维成一个向量),最后的4×4×1代表立体张量(可降…

  周末码一文,明天见矩阵- 其实Numpy之类的单讲特别没意思,但不稍微说下后面说实际应用又不行,所以大家就练练手吧 代码裤子: https://github.com/lotapp/BaseCode 在线编程: https://mybinder.org/v2/gh/lotapp/BaseCode/master 在线地址: http://github.lesschina.com/python/ai/numpy 1.数组定义.常见属性 ¶ 引入一下 Numpy模块, Numpy的数组使用可以查看一…

numpy 简介 numpy的存在使得python拥有强大的矩阵计算能力,不亚于matlab. 官方文档(https://docs.scipy.org/doc/numpy-dev/user/quickstart.html) Quickstart tutorial Prerequisites Before reading this tutorial you should know a bit of Python. If you would like to refresh your memory,…

Quickstart tutorial 引用https://docs.scipy.org/doc/numpy-dev/user/quickstart.html Prerequisites Before reading this tutorial you should know a bit of Python. If you would like to refresh your memory, take a look at the Python tutorial. If you wish to w…

Python Basics with numpy (optional)Welcome to your first (Optional) programming exercise of the deep learning specialization. In this assignment you will: - Learn how to use numpy. - Implement some basic core deep learning functions such as the softm…

Welcome to your first assignment. This exercise gives you a brief introduction to Python. Even if you've used Python before, this will help familiarize you with functions we'll need. Instructions: You will be using Python 3. Avoid using for-loops and…

Python Basics with Numpy (optional assignment) Welcome to your first assignment. This exercise gives you a brief introduction to Python. Even if you've used Python before, this will help familiarize you with functions we'll need. Instructions: You wi…