Section: Elementary Functions
sub2ind function converts a multi-dimensional indexing expression
into a linear (or vector) indexing expression. The syntax for its use
is
y = sub2ind(sizevec,d1,d2,...,dn)
where sizevec is the size of the array being indexed into, and each
di is a vector of the same length, containing index values. The basic
idea behind sub2ind is that it makes
[z(d1(1),d2(1),...,dn(1)),...,z(d1(n),d2(n),...,dn(n))]
equivalent to
z(sub2ind(size(z),d1,d2,...,dn))
where the later form is using vector indexing, and the former one is using native, multi-dimensional indexing.
3 x 4 matrix A containing some random integer
elements
--> A = randi(ones(3,4),10*ones(3,4)) A = 7 9 7 2 8 4 8 2 6 7 10 5 --> quit
We can extract the elements (1,3),(2,3),(3,4) of A via sub2ind.
To calculate which elements of A this corresponds to, we can use
sub2ind as
--> n = sub2ind(size(A),1:3,2:4) n = 4 8 12 --> A(n) ans = 9 8 5 --> quit