libsvm - How to use?

libsvm is a popular library for performing Support Vector Machine algorithm. This library is developed by Chih-Chung Chang and Chih-Jen Lin, professor at National Taiwan University. Next, I will show you how to install the libsvm in MATLAB.

1. Installation

• Step 1. Download the libsvm from http://www.csie.ntu.edu.tw/~cjlin/libsvm/ and unzip it. There are some important files as in the following figure:
  
  

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Useful chunks of MATLAB code

1. Nominal to numeric mapping

The following code will convert from a nominal value vector to a numeric value vector.
Example: suppose that Yno is the nominal value vector and Ynum is the numeric value vector. The casting line is as follow:

Ynum = double(nominal(Yno));

2. Sum one field of a struct

The following code will compute the summation from the field "true" of a struct called "recall".

result=sum(cell2mat({recall.true}));

(Nguyen My - 2015/06/23)

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TỰ TÌNH QUÊ HƯƠNG 1 - NHÀ THƯƠNG MỸ LUÔNG

Quê hương tôi ngày một đổi thay, cái bệnh viện Mỹ Luông ngày nào nay đã thành khu Trung tâm thương mại nhộn nhịp. Hai mươi mấy năm về trước, tôi đã cất tiếng khóc đầu đời tại nơi này. Và cũng chính bởi cái tuổi thơ "nay ốm mai đau" mà cái bệnh viện Mỹ Luông đã thành nơi cho tôi nhiều kỷ niệm không thể nào quên.

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Convert struct of single-value fields into a 2D matrix

Suppose that we have a dataset of N records, each records is a struct of M fields, and each field has just a single numeric value. Now, we want to convert this struct-type dataset into a matrix for further manipulation. What should we do? The following figure will tell you the way:

 Following is the brief description for functions used:

• struct2cell(): converts the m-by-n structure s (with p fields) into a p-by-m-by-n cell array c.
• B=squeeze(A): returns an array B with the same elements as A, but with all singleton dimensions removed.

And here is the sample MATLAB code:

Xstruct = importdata([getCurrentFolder() '\..\data\somename.mat']);
Xcell=struct2cell(Xstruct);
X=squeeze(Xcell)';
X=cell2mat(X);

Thank for reading!

(Nguyen My - 2015/06/16)

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