Matrix

A simple matrix class that's compatible with STL functions and CERNs ROOT library. Includes functions for + - * /, inverting, normalisation, eigenvalues, the trace and transpose. The whole idea of this repository is to have a reusable class for creating and computing matracies that utilise the abilities of STL and is also compatible with CERNs ROOT library for cpp. When viewing and/or using the code please keep in mind I am only a fresh grad and not an experienced software dev, I also have fairly limited knowledge with ROOT so any advice or mistakes that you spot please don't hesitate to contact me.

Prerequisites

Knowledge of C++, ROOT and STL.

Installing

Add the header file to your project, use as you want

Usage

To use the Matrix.h will all the capabilities of ROOT and Eigen::Matrix, you need to include these header files in the Matrix.h underneath my includes. If compiling with root through the commandline there should be no need to include the root library.

To create a matrix, fill it and then output it to console

Creating matrices of different types

// all matrcies are of 5x5, that is 5 rows by 5 columns

// matrix made from default int
matrices::Matrix<int> intMatrix(5, 5);
// uses ROOT Int_t
matrices::Matrix<Int_t> int_tMatrix(5, 5);
// uses default float type
matrices::Matrix<float> floatMatrix(5, 5);
// ROOT Float_t
matrices::Matrix<Float_t> float_tMatrix(5, 5);
// default double
matrices::Matrix<double> doubleMatrix(5, 5);
// ROOT Double_t
matrices::Matrix<Double_t> double_tMatrix(5, 5);

In this example we create an integer matrix, fill it with '5' and then output it to the console.

// create a matrix<int> and fill it
matrices::Matrix<int> matrix(rows, columns);
matrix.fill(5);
std::cout << matrix;

/*
Output:

(5) (5) (5) (5) (5)
(5) (5) (5) (5) (5)
(5) (5) (5) (5) (5)
(5) (5) (5) (5) (5)
(5) (5) (5) (5) (5)
*/

Creating two matrcies then adding them together

matrices::Matrix<int> intMatrixOne(5, 5);
matrices::Matrix<int> intMatrixTwo(5, 5);

intMatrixOne.fill(5);
intMatrixTwo.fill(10);

matrices::Matrix<int> sumOf(5, 5);

sumOf = intMatrixOne + intMatrixTwo;

std::cout << sumOf;

/*
Output:

(15) (15) (15) (15) (15)
(15) (15) (15) (15) (15)
(15) (15) (15) (15) (15)
(15) (15) (15) (15) (15)
(15) (15) (15) (15) (15)
*/

Matrix multiplication

matrices::Matrix<int> productOf(5, 5);
productOf = intMatrixOne * intMatrixTwo;

std::cout << productOf;

/*
Output:

(250) (250) (250) (250) (250)
(250) (250) (250) (250) (250)
(250) (250) (250) (250) (250)
(250) (250) (250) (250) (250)
(250) (250) (250) (250) (250)
*/

Getting the determinant of the martrix. The deteminant will be 0 for this matrix because it has repeating rows

int det = productOf.getDeterminant();
std::cout << det;

/*
Output: 

0
*/

Getting the inverse of the matrix Not fully implemeneted

intMarixOne.invert();

std::cout << intMatrixOne;

/*
Output:


*/

#Compatibility with ROOT

The Matrix class is fully compatible with ROOT TMatrix and ROOT TMatrixT, to convert the matrix from a Matrix to a TMatrixT you only need the .toTMatrixT() function, same as to copy a TMatrixT into a new Matrix you can simply use it in the constructor.

matrices::Matrix<int> matrix(5, 5);
tMatrix.fill(5);

TMatrixT<int> tMatrix = matrix.toTMatrixT();

// to copy the TMatrixT<T> into a new Matrix<T>
TMatrixT<int> newTMatrix; // we're just going to pretend we have data in here
matrices::Matrix<int> newMatrix(newTMatrix);

std::cout << newMatrix;

/*
Output:

The elements within the TMatrixT<T>
*/

Creating histograms from the matrix class, you can easily just create a TH1 from the matrix, it uses each row in the vector to fill the bins

TH1F* newHistF = productOf.toTH1F("TH1F Test", "TH1F Test", 5, 0, 5);
	newHistF->Draw();

Known issues

When using the code it is important to make note that the class is provided as is. I am always welcome to feedback, recommendations for features and bug reports but please do not think this is a professionally made class that is actively maintained. For known issues please refer to the github issues page.

Authors

Felix England

Nuno Taborda

Acknowledgments