Working with matrices

Required include for matrices:

#include <spatium/Matrix.h>

Construct a matrix

The code below constructs the following 2-by-3 matrix:

1 2 3
4 5 6

Method 1: Explicitly by constructor

spatium::Matrix m(2, 3);
m(0,0) = 1; m(0,1) = 2; m(0,2) = 3;
m(1,0) = 4; m(1,1) = 5; m(1,2) = 6;

Method2: Constructor with initalizer list

spatium::Matrix m({{1, 2, 3}, {4, 5, 6}});

Method 3: Implicitly via initalizer list and assignment

spatium::Matrix m = {{1, 2, 3}, {4, 5, 6}};

Implicit conversion

spatium::Matrix m(4, 1);
m(0,0) = 1;
m(1,0) = 2;
m(2,0) = 3;

spatium::Vector3 v = m;

Mathematical operations

Construct the matrix:

spatium::Matrix m1 = {
  { 1, 2, 3 }, 
  { 4, 5, 6}
};

Transpose

spatium::Matrix m2 = m1.transposed();

Result:

1 4
2 5
3 6

Multiply

Multiply by another matrix:

spatium::Matrix m3 = m1 * m2;

Result:

14 32 
32 77

Multiply by scalar

Multiply by scalar 2:

spatium::Matrix m4 = m3 * 2;

Result:

28 64 
64 154

Calculate inverse

spatium::Matrix m5 = {
  {3  , 3.2},
  {3.5, 3.6}
};

Matrix m6 = m5.inverse();

Result:

-9   8
8.75 -7.5

Exception handling

Several functions of class Matrix can throw std::out_of_bounds exception. These are:

• determinant() - If matrix is not square
• inverse() - If matrix is not square or it is singular
• operator()(int, int) - Access element by index - Index out of bounds
• operator+(Matrix) - Add matrices - Dimensions mismatch
• operator+(Matrix) - Subtract matrices - Dimensions mismatch
• operator*(Matrix) - Multiply matrices - Column count mismatch with row count of other matrix

Exception: Accessing element by index

spatium::Matrix matrix = {
  { 1, 2, 3 },
  { 4, 5, 6 }
};

try {
  double val = matrix(1, 3);
}
catch(std::out_of_range e)
{
  // Column range is 0 - 2 (3 is out of bounds)
}