Malab安装libsvm时会遇到的一些坑

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工作环境

• 软件环境：Windows 7 Ultimate sp1、MatlabR2012b 32bit
  

+ c2 k3 {6 T0 z; V; u( r7 o9 Q今天在使用matlab实现svm算法的时候，发现使用svmtrain函数报错：
1 E# a; ]2 q; Y2 SY must be a vector or a character array
7 q3 }: i. r& e: m) k立马help svmtrain看看是否少什么东西，命令执行结果如下：

• help svmtrain
• svmtrain Train a support vector machine classifier
•     SVMSTRUCT = svmtrain(TRAINING, Y) trains a support vector machine (SVM)
•     classifier on data taken from two groups. TRAINING is a numeric matrix
•     of predictor data. Rows of TRAINING correspond to observations; columns
•     correspond to features. Y is a column vector that contains the known
•     class labels for TRAINING. Y is a grouping variable, i.e., it can be a
•     categorical, numeric, or logical vector; a cell vector of strings; or a
•     character matrix with each row representing a class label (see help for
•     groupingvariable). Each element of Y specifies the group the
•     corresponding row of TRAINING belongs to. TRAINING and Y must have the
•     same number of rows. SVMSTRUCT contains information about the trained
•     classifier, including the support vectors, that is used by SVMCLASSIFY
•     for classification. svmtrain treats NaNs, empty strings or 'undefined'
•     values as missing values and ignores the corresponding rows in
•     TRAINING and Y.
•     ........
  

于是，网上找找资料，这一找不得了，发现大问题！按照参考文献的思路，应该是我的Matlab少了libsvm库，搞不好这个问题无解。幸好libsvm不是matlab自带的，而是需要下载编译的，需要的朋友可以从这https://www.csie.ntu.edu.tw/~cjlin/libsvm/下载。

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; R! ~/ U) x5 Y0 A下载下来的是源代码，需要经过编译，查看README.md，可以发现：

• Example:
•         matlab>> mex -setup
•         (ps: MATLAB will show the following messages to setup default compiler.)
•         Please choose your compiler for building external inteRFace (MEX) files:
•         Would you like mex to locate installed compilers [y]/n? y
•         Select a compiler:
•         [1] Microsoft Visual C/C++ version 7.1 in C:\Program Files\Microsoft Visual Studio
•         [0] None
•         Compiler: 1
•         Please verify your choices:
•         Compiler: Microsoft Visual C/C++ 7.1
•         Location: C:\Program Files\Microsoft Visual Studio
•         Are these correct?([y]/n): y
•         matlab>> make
• On Unix systems, if neither make.m nor 'mex -setup' works, please use
• Makefile and type 'make' in a command window. Note that we assume
• your MATLAB is installed in '/usr/local/matlab'. If not, please change
• MATLABDIR in Makefile.
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# i0 m8 [3 V0 y3 _: O$ q* U于是赶紧将libsvm压缩包扔到matlab/toolbox/下面，然后定位到libsvm3.23文件夹，输入mex -setup，

• Select a compiler:
• [1] Lcc-win32 C 2.4.1 in E:\1_PROG~1\MATLAB~1\sys\lcc
• [0] None
• Compiler: mex -setup
• Please select from 0-1
• Compiler:
• Please select from 0-1
• Compiler: 1
• Please verify your choices:
• Compiler: Lcc-win32 C 2.4.1
• Location: E:\1_PROG~1\MATLAB~1\sys\lcc
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只有一个编译器！也就是matlab自带的编译器，于是只能选择该编译器，输入make，出来一堆错误：
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• >> make
• Error ..\svm.cpp: 15  syntax error; found `<' expecting `;'
• Error ..\svm.cpp: 15  skipping `<'
• Error ..\svm.cpp: 15  syntax error; found `T' expecting `;'
• Error ..\svm.cpp: 15  syntax error; found `>' expecting `;'
• Error ..\svm.cpp: 15  skipping `>'
• Error ..\svm.cpp: 15  syntax error; found `T' expecting `;'
• Error ..\svm.cpp: 15  syntax error; found `min' expecting `;'
• Error ..\svm.cpp: 15  syntax error; found `x' expecting `)'
• Error ..\svm.cpp: 15  skipping `x' `,' `T' `y'
• Error ..\svm.cpp: 15  undeclared identifier `x'
• Error ..\svm.cpp: 15  undeclared identifier `y'
• Warning ..\svm.cpp: 15   possible usage of x before definition
• Warning ..\svm.cpp: 15   possible usage of y before definition
• Error ..\svm.cpp: 18  syntax error; found `<' expecting `;'
• Error ..\svm.cpp: 18  skipping `<'
• Error ..\svm.cpp: 18  syntax error; found `T' expecting `;'
• Error ..\svm.cpp: 18  syntax error; found `>' expecting `;'
• Error ..\svm.cpp: 18  skipping `>'
• Error ..\svm.cpp: 18  syntax error; found `T' expecting `;'
• Error ..\svm.cpp: 18  syntax error; found `max' expecting `;'
• Error ..\svm.cpp: 18  syntax error; found `x' expecting `)'
• Error ..\svm.cpp: 18  skipping `x' `,' `T' `y'
• Error ..\svm.cpp: 18  too many errors
•   E:\1_PROG~1\MATLAB~1\BIN\MEX.PL: Error: Compile of '..\svm.cpp' failed.
• Error: E:\1_Program_File\MatlabR2012b\toolbox\matlab\general\mex.m failed (line 206)
• Unable to complete successfully.
• => Please check README for detailed instructions.
  

  
; L# ]# x; V* h1 E4 T( }原因是lcc 编译器不支持c++，要使得matlab能够编译c++文件的话，只能安装第三方编译器比如微软的vsstudio或者vc++6.0以及mingw-w64，由于vs或者vc比较大我就没再折腾，倒是下载了mingw-w64的离线版，（在线安装版本下载不下来），但是离线版下载下来之后解压缩，死活都配置不好，matlab中就是不显示该编译器！我电脑中其实也有一个cl编译器也不了解如何去配置。最后无果，只能找一个编译好的libsvm32位版本，据说是在winxp下面编译的，通用性应该不错，试了试，可以成功运行！


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Malab安装libsvm时的一些坑