Finding an index from a 3D matrix

Hello,

I am writing to ask for help in finding the index of a point in a 3D array. I have a 3D matrix of dimentions [M,N,O] and I have reshaped it onto a 1xQ array (Q = M*N*O)

I'm trying to find the index in array Q of a point selected three dimensionally in the MNO matrix. This could easily be performed in 2D ith the 'sub2ind()' function, but I havent been able to do this in 3D.

I would apreciate any help.

Best,

Alonso

Answer 1

[Dyuman Joshi]

sub2ind works for 3D arrays as well

%Initial array, with random values for example
in = reshape(1:105,3,5,7);
%Array reshaped into a row vector
out = reshape(in,1,[]);
%Random point in the 3D array
ix = randi(3)

ix = 2

iy = randi(5)

iy = 1

iz = randi(7)

iz = 6

linearindex = sub2ind(size(in), ix, iy, iz)

linearindex = 77

%Verifying the answer as our data is simply 1:numel(in)
in(ix, iy, iz)

ans = 77