凯鲁嘎吉
用书写铭记日常,最迷人的不在远方

浅谈范数正则化

    作者:凯鲁嘎吉 - 博客园 http://www.cnblogs.com/kailugaji/

    这篇博客介绍不同范数作为正则化项时的作用。首先介绍了常见的向量范数与矩阵范数,然后说明添加正则化项的原因,之后介绍向量的$L_0$,$L_1$,$L_2$范数及其作为正则化项的作用,对三者进行比较分析,并用贝叶斯观点解释传统线性模型与正则化项。随后,介绍矩阵的$L_{2, 1}$范数及其推广形式$L_{p, q}$范数,以及矩阵的核范数及其推广形式Schatten范数。最后,用MATLAB程序编写了Laplace分布与Gauss分布的概率密度函数图。有关矩阵范数优化求解问题可参考:一类涉及矩阵范数的优化问题 - 凯鲁嘎吉 - 博客园 

1. 向量范数与矩阵范数

2. 为什么要添加正则项?

3. $L_0$范数

4. $L_1$范数

5. $L_2$范数

6. $L_1$范数与$L_2$范数作为正则项的区别

7. 用概率解释传统线性回归模型

8. $L_2$范等价于Gauss先验

9. $L_1$范数等价于Laplace先验

10. 矩阵的$L_{2, 1}$范数及$L_{p, q}$范数

11. 矩阵的核范数及Schatten范数

12. MATLAB程序:Laplace分布与Gauss分布的概率密度函数图

%% Demo of Laplace Density Function
% x : variable
% lambda : size para
%miu: location para
clear
clc
x = -10:0.1:10;
y_1=Laplace_distribution(x, 0, 1);
y_2=Laplace_distribution(x, 0, 2);
y_3=Laplace_distribution(x, 0, 4);
y_4=Laplace_distribution(x, -5, 4);
y_5=Laplace_distribution(x, 5, 4);
y_6=normpdf(x,0,1);
plot(x, y_1, 'r-', x, y_2, 'g-', x, y_3, 'c-', x, y_4, 'm-', x, y_5, 'y-', x, y_6, 'b-', 'LineWidth',1.2);
legend('\mu =0, \lambda=1','\mu=0, \lambda=2','\mu=0, \lambda=4','\mu=-5, \lambda=4','\mu=5, \lambda=4', '\mu=0, \sigma=1'); %图例的设置
xlabel('x');
ylabel('f(x)');
title('Laplace vs Gauss pdf');
set(gca, 'FontName', 'Times New Roman', 'FontSize',11);
saveas(gcf,sprintf('demo_Laplace_Gauss.jpg'),'bmp'); %保存图片

%% Laplace Density Function
function y=Laplace_distribution(x, miu, lambda)
    y = 1 / (2*lambda) * exp( -abs(x-miu)/lambda);
end

13. 参考文献

[1] 证明核范数是矩阵秩的凸包络

EJ Candès,  Recht B . Exact Matrix Completion via Convex Optimization[J]. Foundations of Computational Mathematics, 2009, 9(6):717.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.312.1183&rep=rep1&type=pdf

[2] 关于说明$L_1$范数是$L_0$范数的凸包络的文献及教案

Donoho D L ,  Huo X . Uncertainty Principles and Ideal Atomic Decomposition[J]. IEEE Transactions on Information Theory, 2001, 47(7):2845-2862.

http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=00BC0C50CDECB265657379792F917FFE?doi=10.1.1.161.9300&rep=rep1&type=pdf

Learning with Combinatorial Structure Note for Lecture 12

http://people.csail.mit.edu/stefje/fall15/notes_lecture12.pdf

L1-norm Methods for Convex-Cardinality Problems

https://web.stanford.edu/class/ee364b/lectures/l1_slides.pdf

[3] 有关过拟合的教案及图片来源

2017 Lecture 2: Overfitting. Regularization

https://www.cs.mcgill.ca/~dprecup/courses/ML/Lectures/ml-lecture02.pdf

[4] 一些可供参考的资料

The difference between L1 and L2 regularization

https://explained.ai/regularization/L1vsL2.html

Why L1 norm for sparse models

https://stats.stackexchange.com/questions/45643/why-l1-norm-for-sparse-models

Why L1 regularization can “zero out the weights” and therefore leads to sparse models? [duplicate]

https://stats.stackexchange.com/questions/375374/why-l1-regularization-can-zero-out-the-weights-and-therefore-leads-to-sparse-m

What are L1, L2 and Elastic Net Regularization in neural networks?

https://www.machinecurve.com/index.php/2020/01/21/what-are-l1-l2-and-elastic-net-regularization-in-neural-networks/

Introduction. Sharpness Enhancement and Denoising of Image Using L1-Norm Minimization Technique in Adaptive Bilateral Filter. 

https://www.ijsr.net/archive/v3i11/T0NUMTQxMzUy.pdf

posted on 2021-04-08 16:58  凯鲁嘎吉  阅读(2701)  评论(2编辑  收藏  举报