MATLAB: Sparse Matrix, struct, structure, Using cell arrays

Question

A sparse matrix is a large Matrix with almost all elements of the same value (typically zero). The normal representation of a spark Matrix takes up lots of memory when useful information can be captured with much less. A possible way to represent a sparse matrix is with a cell vector whose first element is a 2-element vector representing the size of the sparse matrix. The second element is a scalar specifying the default value of the sparse matrix. Each successive element of the cell vector is a 3-element vector representing one element of sparse matrix that has a value other than default. The three elements row index, the column index and the actual value. Write a function called sparse2matrix that takes a single input of a cell vector as defined above and returns the output argument called matrix, the matrix in its traditional form. Consider the following run:

cellvec = {[2 3], 0, [1 2 3], [2 2 -3]};
matrix = sparse2matrix(cellvec)
matrix =
    0        3        0
    0       -3        0 

Answer 1

function matrix=sparse2matrix(cellvec)
matrix=cellvec{1,2}*ones(cellvec{1,1});
[m n]=size(cellvec);
for i=3:n
    A=cellvec{1,i};
    p=A(1);
    q=A(2);
    matrix(p,q)=A(3);
end
end