Eigen matrix helper functions - from and to std::vector and from and to file (Qt)

eigen_matrix_helper.cpp

template<typename Scalar, typename Container>
inline static Eigen::Matrix<Scalar,-1,-1> toEigenMatrix( const Container& vectors ){
	typedef typename Container::value_type VectorType;
	typedef typename VectorType::value_type Scalar;
	Eigen::Matrix<Scalar,-1,-1> M(vectors.size(), vectors.front().size());
	for(size_t i = 0; i < vectors.size(); i++)
		for(size_t j = 0; j < vectors.front().size(); j++)
			M(i,j) = vectors[i][j];
	return M;
}

template<typename Scalar, typename Matrix>
inline static std::vector< std::vector<Scalar> > fromEigenMatrix( const Matrix & M ){
	std::vector< std::vector<Scalar> > m;
	m.resize(M.rows(), std::vector<Scalar>(M.cols(), 0));
	for(size_t i = 0; i < m.size(); i++)
		for(size_t j = 0; j < m.front().size(); j++)
			m[i][j] = M(i,j);
	return m;
}

// Input / output Eigen matrix from / to disk
#include <QFileInfo>
#include <QTextStream>
static inline Eigen::MatrixXd matrixFromFile( QString filename, QString splitChar = "," )
{
	Eigen::MatrixXd M;

	// Read data
	QFile file( filename );
	if(!file.open(QFile::ReadOnly | QFile::Text)) return M;
	std::vector< std::vector<double> > mat;
	QTextStream in(&file);
	QStringList lines = in.readAll().split('\n');
	for( auto line : lines ){
		auto row_string = line.split(splitChar, QString::SkipEmptyParts);
		if(row_string.size() < 1) continue;

		std::vector<double> row;
		for(auto token : row_string) 
			row.push_back(token.toDouble());
		mat.push_back( row );
	}

	// Copy values
	M = Eigen::MatrixXd(mat.size(), mat.front().size());
	for(size_t i = 0; i < mat.size(); i++){
		for(size_t j = 0; j < mat.front().size(); j++){
			M(i,j) = mat[i][j];
		}
	}

	return M;
}

static inline void matrixToFile(const Eigen::MatrixXd & M, QString filename){
	QFile file( filename );
	if(!file.open(QFile::WriteOnly | QFile::Text)) return;
	QTextStream out(&file);
	for(unsigned int i = 0; i < M.rows(); i++)
	{
		QStringList row;
		for(unsigned int j = 0; j < M.cols(); j++)
			row << QString::number(M(i,j));
		out << (row.join(",") + "\n");
	}
}