# HG changeset patch
# User jwe
# Date 867263850 0
# Node ID 1a5fe3010f09efcf57f2e34fe5f019e208d790b3
# Parent  9c6cd52f3f5a9089d58f0764281b4d6db176dbe3
[project @ 1997-06-25 18:36:19 by jwe]

diff --git a/scripts/ChangeLog b/scripts/ChangeLog
--- a/scripts/ChangeLog
+++ b/scripts/ChangeLog
@@ -1,3 +1,12 @@
+Wed Jun 25 13:34:06 1997  John W. Eaton  <jwe@bevo.che.wisc.edu>
+
+	* polynomial/polyfit.m: Return fit y values as second output.
+	Don't use QR factorization to solve least squares problem.
+
+Wed Jun 18 10:24:00 1997  John W. Eaton  <jwe@bevo.che.wisc.edu>
+
+	* control/dlqr.m: Use ao, not a, to compute k.
+
 Tue Jun  3 12:16:00 1997  John W. Eaton  <jwe@bevo.che.wisc.edu>
 
 	* miscellaneous/path.m: New file.
diff --git a/scripts/control/dlqr.m b/scripts/control/dlqr.m
--- a/scripts/control/dlqr.m
+++ b/scripts/control/dlqr.m
@@ -92,7 +92,7 @@
   if (is_symmetric (q) && is_symmetric (r) ...
       && all (eig (q) >= 0) && all (eig (r) > 0))
     p = dare (ao, b, qo, r);
-    k = (r+b'*p*b)\b'*p*a + r\zz';
+    k = (r+b'*p*b)\b'*p*ao + r\zz';
     e = eig (a - b*k);
   else
     error ("dlqr: q (r) must be symmetric positive (semi) definite");
diff --git a/scripts/polynomial/polyfit.m b/scripts/polynomial/polyfit.m
--- a/scripts/polynomial/polyfit.m
+++ b/scripts/polynomial/polyfit.m
@@ -17,17 +17,20 @@
 ## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
 ## 02111-1307, USA.
 
-## usage:  polyfit (x, y, n)
+## usage:  [p, yf] = polyfit (x, y, n)
 ##
 ## Returns the coefficients of a polynomial p(x) of degree n that
 ## minimizes sumsq (p(x(i)) - y(i)), i.e., that best fits the data
 ## in the least squares sense.
+##
+## If two outputs are requested, also return the values of the
+## polynomial for each value of x.
 
 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
 ## Created: 13 December 1994
 ## Adapted-By: jwe
 
-function p = polyfit (x, y, n)
+function [p, yf] = polyfit (x, y, n)
 
 
   if (nargin != 3)
@@ -46,22 +49,26 @@
   x = reshape (x, l, 1);
   y = reshape (y, l, 1);
 
-  X = ones (l, 1);
+  ## Unfortunately, the economy QR factorization doesn't really save
+  ## memory doing the computation -- the returned values are just
+  ## smaller.
 
-  if (n > 0)
-    tmp = (x * ones (1, n)) .^ (ones (l, 1) * (1 : n));
-    X = [X, tmp];
-  endif
+  ## [Q, R] = qr (X, 0);
+  ## p = flipud (R \ (Q' * y));
 
-  ## Compute polynomial coeffients, making returned value compatible
-  ## with Matlab.
+  ## XXX FIXME XXX -- this is probably not so good for extreme values of
+  ## N or X...
 
-  [Q, R] = qr (X, 0);
+  X = (x * ones (1, n+1)) .^ (ones (l, 1) * (0 : n));
 
-  p = flipud (R \ (Q' * y));
+  p = (X' * X) \ (X' * y);
 
   if (! prefer_column_vectors)
     p = p';
   endif
 
+  if (nargout == 2)
+    yf = X * p;
+  endif
+
 endfunction