# HG changeset patch
# User Jaroslav Hajek <highegg@gmail.com>
# Date 1238156341 -3600
# Node ID a1635f7c4cbeaf758dfde892c2a34bc1ae1d8532
# Parent  88bf56bbccca84f1800b460559bd8f3c7b07cb76
update diag-perm.txi

diff -r 88bf56bbccca -r a1635f7c4cbe doc/ChangeLog
--- a/doc/ChangeLog	Fri Mar 27 12:22:05 2009 +0100
+++ b/doc/ChangeLog	Fri Mar 27 13:19:01 2009 +0100
@@ -1,3 +1,7 @@
+2009-03-27  Jaroslav Hajek  <highegg@gmail.com>
+
+	* interpreter/diagperm.txi: Mention mixing with sparse matrices.
+
 2009-03-25  John W. Eaton  <jwe@octave.org>
 
 	* interpreter/munge-texi.cc (process_texi_input_file):
diff -r 88bf56bbccca -r a1635f7c4cbe doc/interpreter/diagperm.txi
--- a/doc/interpreter/diagperm.txi	Fri Mar 27 12:22:05 2009 +0100
+++ b/doc/interpreter/diagperm.txi	Fri Mar 27 13:19:01 2009 +0100
@@ -258,6 +258,12 @@
 happens to be diagonal (an is thus not a special object) is of course treated
 normally.
 
+Multiplication and division by diagonal matrices works efficiently also when
+combined with sparse matrices, i.e. @code{D*S}, where @var{D} is a diagonal
+matrix and @var{S} is a sparse matrix scales the rows of the sparse matrix and
+returns a sparse matrix. The expressions @code{S*D}, @code{D\S}, @code{S/D} work
+analogically.
+
 If @var{D1} and @var{D2} are both diagonal matrices, then the expressions
 @example
 D1 + D2
@@ -320,6 +326,12 @@
 flag internally, and thus the choice between the two above equivalent
 expressions for inverse permuting is completely up to the user's taste.
 
+Multiplication and division by permutation matrices works efficiently also when
+combined with sparse matrices, i.e. @code{P*S}, where @var{P} is a permutation
+matrix and @var{S} is a sparse matrix permutes the rows of the sparse matrix and
+returns a sparse matrix. The expressions @code{S*P}, @code{P\S}, @code{S/P} work
+analogically.
+
 Two permutation matrices can be multiplied or divided (if their sizes match), performing
 a composition of permutations. Also a permutation matrix can be indexed by a permutation
 vector (or two vectors), giving again a permutation matrix.
@@ -351,6 +363,8 @@
 @dfn{abs}, @dfn{real}, @dfn{imag}, @dfn{conj}, @dfn{sqrt}. 
 A diagonal matrix can also be returned from the @dfn{balance}
 and @dfn{svd} functions.
+The @dfn{sparse} function will convert a diagonal matrix efficiently to a
+sparse matrix.
 
 @node Permutation Matrix Functions
 @subsection Permutation Matrix Functions
@@ -362,6 +376,11 @@
 A permutation matrix can also be returned from the built-in functions
 @dfn{lu} and @dfn{qr}, if a pivoted factorization is requested.
 
+The @dfn{sparse} function will convert a permutation matrix efficiently to a
+sparse matrix.
+The @dfn{find} function will also work efficiently with a permutation matrix,
+making it possible to conveniently obtain the permutation indices.
+
 @node Example Codes
 @section Some Examples of Usage