** Express a least squares problem as a larger linear system. **

** S = SPAUGMENT(A,c) creates the sparse, square, symmetric indefinite **

** matrix S = [c* I A; A' 0]. This matrix is related to the least **

** squares problem **

** min norm(b - A*x) **

** by **

** r = b - A*x **

** S * [r/c; x] = [b; 0]. **

** **

** **

** The optimum value of the residual scaling factor c, involves **

** min(svd(A)) and norm(r), which are usually too expensive to compute. **

** S = SPAUGMENT(A), without a specified value of c, uses the **

** default set by SPPARMS , which is usually max(max(abs(A)))/1000. **

** **

** **

** The augmented matrix is used automatically by the sparse **

** linear equation solvers, \ and /, for nonsquare problems. **

** **

** **

** See also SPPARMS . **

** **