--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mftoolbox/sqrtm_newton_full.m	Wed May 06 14:56:53 2015 +0200
@@ -0,0 +1,26 @@
+function [X,k] = sqrtm_newton_full(A, X0)
+%SQRTM_NEWTON_FULL   Matrix square root by full Newton method.
+%   [X,K] = SQRTM_NEWTON_FULL(A, X0) applies Newton's method to
+%   compute a square root X of the matrix A, with starting matrix X0.
+%   Default: X0 = A.  K is the number of iterations.
+
+if nargin < 2, X0 = A; end
+
+X = X0;
+tol = mft_tolerance(A);
+maxit = 50;
+
+for k = 1:maxit
+
+   Xold = X;
+   R = A - X^2;
+   % Solve XE + EX = R.
+   E = sylvsol(X,X,R);
+   X = X + E;
+
+   reldiff = norm(X - Xold,inf)/norm(X,inf);
+
+   if reldiff <= tol; return; end
+
+end
+error('Not converged after %2.0f iterations', maxit)