C++矩阵处理工具——Eigen .

Eigen是C++中可以用来调用并进行矩阵计算的一个库，里面封装了一些类，需要的头文件和功能如下：

 

Eigen的配置

 

Eigen的应用举例：

Eigen下载地址

Eigen的应用举例：整理的一些常用操作，基本的矩阵运算就在下面了，算是个入门吧~主要分以下几部分：

建议大家放到编译环境里去看，因为我这里有一些region的东西，编译器下更方便看~

#include <iostream>#include <Eigen/Dense>//using Eigen::MatrixXd;using namespace Eigen;using namespace Eigen::internal;using namespace Eigen::Architecture;using namespace std;int main(){#pragma region one_d_objectcout<<"*******************1D-object****************"<<endl;Vector4d v1;v1<< 1,2,3,4;cout<<"v1=\n"<<v1<<endl;VectorXd v2(3);v2<<1,2,3;cout<<"v2=\n"<<v2<<endl;Array4i v3;v3<<1,2,3,4;cout<<"v3=\n"<<v3<<endl;ArrayXf v4(3);v4<<1,2,3;cout<<"v4=\n"<<v4<<endl;#pragma endregion#pragma region two_d_objectcout<<"*******************2D-object****************"<<endl;//2D objects:MatrixXd m(2,2);//method 1m(0,0) = 3;m(1,0) = 2.5;m(0,1) = -1;m(1,1) = m(1,0) + m(0,1);//method 2m<<3,-1,2.5,-1.5;cout <<"m=\n"<< m << endl;#pragma endregion#pragma region Comma_initializercout<<"*******************Initialization****************"<<endl;int rows=5;int cols=5;MatrixXf m1(rows,cols);m1<<( Matrix3f()<<1,2,3,4,5,6,7,8,9 ).finished(),MatrixXf::Zero(3,cols-3),MatrixXf::Zero(rows-3,3),MatrixXf::Identity(rows-3,cols-3);cout<<"m1=\n"<<m1<<endl;#pragma endregion#pragma region Runtime_infocout<<"*******************Runtime Info****************"<<endl;MatrixXf m2(5,4);m2<<MatrixXf::Identity(5,4);cout<<"m2=\n"<<m2<<endl;MatrixXf m3;m3=m1*m2;cout<<"m3.rows()="<<m3.rows()<<"  ;  "     <<"m3.cols()="<< m3.cols()<<endl;cout<<"m3=\n"<<m3<<endl;#pragma endregion#pragma region Resizingcout<<"*******************Resizing****************"<<endl;//1D-resizev1.resize(4);cout<<"Recover v1 to 4*1 array : v1=\n"<<v1<<endl;//2D-resizem.resize(2,3);m.resize(Eigen::NoChange, 3);m.resizeLike(m2);m.resize(2,2);#pragma endregion#pragma region Coeff_accesscout<<"*******************Coefficient access****************"<<endl;float tx=v1(1);tx=m1(1,1);cout<<endl;#pragma endregion#pragma  region Predefined_matrixcout<<"*******************Predefined Matrix****************"<<endl;//1D-objecttypedef  Matrix3f   FixedXD;FixedXD x;x=FixedXD::Zero();x=FixedXD::Ones();x=FixedXD::Constant(tx);//tx is the valuex=FixedXD::Random();cout<<"x=\n"<<x<<endl;typedef ArrayXf Dynamic1D;//或者 typedef VectorXf Dynamic1Dint size=3;Dynamic1D xx;xx=Dynamic1D::Zero(size);xx=Dynamic1D::Ones(size);xx=Dynamic1D::Constant(size,tx);xx=Dynamic1D::Random(size);cout<<"xx=\n"<<x<<endl;//2D-objecttypedef MatrixXf Dynamic2D;Dynamic2D y;y=Dynamic2D::Zero(rows,cols);y=Dynamic2D::Ones(rows,cols);y=Dynamic2D::Constant(rows,cols,tx);//tx is the valuey=Dynamic2D::Random(rows,cols);#pragma endregion#pragma region Arithmetic_Operatorscout<<"******************* Arithmetic_Operators****************"<<endl;//add & subMatrixXf m4(5,4);MatrixXf m5;m4=m2+m3;m3-=m2;//productm3=m1*m2; //transpositionm5=m4.transpose();//m5=m.adjoint();//伴随矩阵//dot productdouble xtt;cout<<"v1=\n"<<v1<<endl;v2.resize(4);v2<<VectorXd::Ones(4);cout<<"v2=\n"<<v2<<endl;cout<<"*************dot product*************"<<endl;xtt=v1.dot(v2);cout<<"v1.*v2="<<xtt<<endl;//vector normcout<<"*************matrix norm*************"<<endl;xtt=v1.norm();cout<<"norm of v1="<<xtt<<endl;xtt=v1.squaredNorm();cout<<"SquareNorm of v1="<<xtt<<endl;#pragma endregioncout<<endl;}