ndgrid() what does it do in matlab

In Matlab, ndgrid() is a function that is used to generate a grid of coordinates for n-dimensional matrices. It is similar to the meshgrid() function, but can handle multi-dimensional arrays.

Suppose we have a 2-dimensional matrix defined as:

main.m
A = [1 2 3;
     4 5 6;
     7 8 9];
37 chars
4 lines

We can use ndgrid() on matrix A to create two matrices X and Y:

main.m
[X, Y] = ndgrid(1:size(A, 1), 1:size(A, 2))
44 chars
2 lines

This will create two matrices X and Y:

main.m
X = [1 1 1;
     2 2 2;
     3 3 3]

Y = [1 2 3;
     1 2 3;
     1 2 3]
73 chars
8 lines

The X matrix represents the row indices of the original matrix, and Y matrix represents the column indices. The value of X(i,j) represents the row index for the element at position (i,j) in the original matrix. Similarly, the value of Y(i,j) represents the column index for the element at position (i,j) in the original matrix.

We can use these matrices X and Y to perform computations and calculations that involve computing a function over a range of values.

Note that ndgrid() can handle any number of dimensions. If we have a 3-dimensional matrix B, then we can use ndgrid() to create three matrices X, Y, and Z, where X represents the row index, Y represents the column index, and Z represents the third dimension index.

Reference: MathWorks Documentation