MATLAB: How to perform matrix calculations with operators

large matrixleast-squarelsqlinoperator

I want to solve a least square problem, say with \ or lsqlin. My matrix C is huge, so I want to represent it with an operator. I have defined "mtimes" and "ctranspose" for my operator, so C*x and C'*x are defined, but I don't know how to do "mldivide".
Generally, how do Matlab functions [that accept matrices as input] work with operators? (say eigs, or lsqlin, …)
Specifically, my question is how should I do something like this:
A = myOperator(parameter1, parameter2);
x = im2double(imread('cameraman.tif'));
y = imnoise(x, 'gaussian' , 0,0.01);
y = y(:);
g = lsqlin(A,y);
As I said, A*x(:) and A'*x(:) are defined.
Any help is appreciated.

Best Answer

You could try calling one of the sparse iterative linear solvers as the "workhorse" behind your object's implementation of MLDIVIDE. Each of them can accept a function handle instead of a matrix as the coefficient matrix representing the system to be solved. See the description of each individual solver to learn what that function handle needs to return to the solver, usually either A*x or A'*x and sometimes both based on a flag.
Related Question