# HG changeset patch
# User Jaroslav Hajek <highegg@gmail.com>
# Date 1280386283 -7200
# Node ID 1646bd8e37359029ff20f62e9b26170b2dbec703
# Parent  b4ebfd6753218d23ecc73dfc0567e6a769ece6f6
special case diagonal matrices and scalars in expm

diff --git a/scripts/ChangeLog b/scripts/ChangeLog
--- a/scripts/ChangeLog
+++ b/scripts/ChangeLog
@@ -1,3 +1,8 @@
+2010-07-29  Jaroslav Hajek  <highegg@gmail.com>
+
+	* linear-algebra/expm.m: Special-case scalars and diagonal matrices.
+	Suggested by M. Caliari.
+
 2010-07-26  Rik <octave@nomad.inbox5.com>
 
 	* linear-algebra/logm.m: Improve documentation string.  Add GPL header.
diff --git a/scripts/linear-algebra/expm.m b/scripts/linear-algebra/expm.m
--- a/scripts/linear-algebra/expm.m
+++ b/scripts/linear-algebra/expm.m
@@ -76,6 +76,14 @@
     error ("expm: input must be a square matrix");
   endif
 
+  if (isscalar (a))
+    r = exp (a);
+    return
+  elseif (strfind (typeinfo (a), "diagonal matrix"))
+    r = diag (exp (diag (a)));
+    return
+  endif
+
   n = rows (a);
   ## Trace reduction.
   a(a == -Inf) = -realmax;