From: Michael Orlitzky <michael@orlitzky.com>
Date: Wed, 19 Feb 2014 00:51:18 +0000 (-0500)
Subject: Fix the column matrix 1-norm (it was missing the absolute value).
X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=1e50b14bbdb48fbb63c487c66f5594fa20d58350;p=numerical-analysis.git

Fix the column matrix 1-norm (it was missing the absolute value).
---

diff --git a/src/Linear/Matrix.hs b/src/Linear/Matrix.hs
index 2422eef..90a97b2 100644
--- a/src/Linear/Matrix.hs
+++ b/src/Linear/Matrix.hs
@@ -579,7 +579,8 @@ instance (Ring.C a, Arity m, Arity n) => Module.C a (Mat m n a) where
   x *> (Mat rows) = Mat $ V.map (V.map (NP.* x)) rows
 
 
-instance (Algebraic.C a,
+instance (Absolute.C a,
+          Algebraic.C a,
           ToRational.C a,
           Arity m)
          => Normed (Mat (S m) N1 a) where
@@ -594,8 +595,12 @@ instance (Algebraic.C a,
   --   >>> norm_p 2 v1
   --   5.0
   --
+  --   >>> let v1 = vec2d (-1,1) :: Col2 Double
+  --   >>> norm_p 1 v1 :: Double
+  --   2.0
+  --
   norm_p p (Mat rows) =
-    (root p') $ sum [fromRational' (toRational x)^p' | x <- xs]
+    (root p') $ sum [fromRational' (toRational $ abs x)^p' | x <- xs]
     where
       p' = toInteger p
       xs = concat $ V.toList $ V.map V.toList rows