Question

How can you implement multidimensional arrays in Armadillo, and what are the common operations you can perform on them?

Answer 1

In Armadillo, multidimensional arrays are implemented using field or cube classes. Field class is more flexible as it can store different types and sizes of matrices, while cube class stores 3D arrays with fixed dimensions.

To create a cube:

#include <armadillo>

using namespace arma;

cube myCube(sizeX, sizeY, sizeZ);

For fields:

field<mat> myField(numOfMatrices);

myField(0) = mat(sizeX, sizeY);

Common operations on cubes include element-wise addition, subtraction, multiplication, division, and slicing. For example:

1. Addition: 

resultCube = cubeA + cubeB;

2. Subtraction: 

resultCube = cubeA - cubeB;

3. Element-wise multiplication: 

resultCube = cubeA % cubeB;

4. Element-wise division: 

resultCube = cubeA / cubeB;

5. Slicing: 

mat sliceXY = myCube.slice(sliceIndex);

Operations on fields involve iterating through the field to perform matrix operations like addition, subtraction, multiplication, etc., using standard Armadillo functions.