sub2ind() converts subscripts to linear indices.
Say for example, you have a mxn matrix, and you want to find the linear index of (i,j)th element (given i<=m, j<=n). (Linear indexing in MATLAB is done column wise.) sub2ind() will be useful for that
%Random values
m=randi(7);
n=randi(7);
y=rand(m,n);
%As stated above, an example of Linear indexing
out=reshape(1:m*n,m,n)
%You want to find the linear index of (2,3)
%Syntax is sub2ind(sizeofthematrix,rowindex,columnindex)
ind=sub2ind(size(y),2,3)
%Verification
out(2,3)
Now
['sub2ind(ngrid.*ones(1,ndim)' idnames ');']
%updates to
['sub2ind(ngrid.*ones(1,ndim),1,20);']
%As [] is a concatenation operator
so
x=3;y=2;z=1;
eval('x+y-z')
%is equivalent to
x+y-z
%In terms of the above example, it is equivalent to
sub2ind(ngrid.*ones(1,ndim),1,20)
%which is equal to
sub2ind(20.*[1 1],1,20)
%i.e. the linear index of (1,20) in a 20x20 matrix,
%and thus you get the value 381
Hope this is helpful.
