/** \file

* \brief An example Eigen program.

*

* \mainpage This code showcases Eigen (a linear algebra package).

* When called with no prameters, it rotates a triangle.

* When given a filename containing one white-space-separted, 2D vector,

* the points are rotated.

* \author Nick Vence

* \date 09/10/2013

**/

#include<iostream>

using std::cout;

using std::endl;

#include<fstream>

using std::ifstream;

#include<cmath>

using std::sin;

using std::cos;

#include<Eigen/Dense>

using Eigen::Matrix;

using Eigen::Matrix2f;

using Eigen::Vector2f;

using Eigen::Dynamic;

///rot() creates a 2D rotation matrix about an angle TH.

///\param TH theta, the angle of rotation

Matrix2f rot(float th) {

float sinTH = sin(th);

float cosTH = cos(th);

Matrix2f rot;

rot << cosTH, -sinTH,

sinTH, cosTH;

return rot;

}

/// If( argv[1] ) load vectors,

/// otherwise rotate a triangle.

int main(int argc, char* argv[]) {

if(argc == 1) {

Matrix<float,2,3> pts;

pts << 1, 0, 1,

0, 1, 1;

cout << pts << endl;

cout << "After rotating 45 degrees" << cout.precision(3) << endl;

cout << rot(M_PI/4) * pts << endl;

cout << "After rotating 90 degrees" << endl;

cout << rot(M_PI/2) * pts << endl;

cout << "Enter a filename of tab separated values" << endl;

} else {

/// Counting nVec: the number of vectors in filename.

ifstream file;

file.open(argv[1]);

int nVec = 0;

float x, y;

while( file >> x >> y) nVec++;

cout << "nVec = " << nVec << endl;

Matrix<float, 2, Dynamic> v(2,nVec);

file.close();

///Load v: data vector

file.open(argv[1]);

for(int i=0; file >> x >> y; i++) {

v(0,i) = x;

v(1,i) = y;

}

cout << "v = " << endl;

cout << v << endl;

file.close();

///Rotate points

const int nTH = 6;

for( int i=0; i<nTH; i++) {

float TH = i*M_PI / (2*nTH);

printf( "%.2f =================\n", TH);

for( int j=0; j < nVec; j++) {

Vector2f v1 = rot(TH) * v.col(j);

printf("% 6f\t% 6f\n", v1(0), v1(1));

}

}

}

return 0;

}