Returns the position in the matrix of a given point. Dedicated to 2 dimensions structures.
L = localise2d(t)
the index of the node (between 1 and npoints). We can pass several points at the same time.
the index (2 values because we are in 2 dimensions) of the corresponding node in the matrix.
Returns the position in the matrix of a given point. Dedicated to 2 dimensions structures.