From: Michael Orlitzky <michael@orlitzky.com>
Date: Tue, 16 Oct 2012 02:16:13 +0000 (-0400)
Subject: Negate the poisson matrix during its generation.
X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=2fbcf94908d646ec62d2f15f7ec35288c6ac1cfe;p=octave.git

Negate the poisson matrix during its generation.
---

diff --git a/poisson_matrix.m b/poisson_matrix.m
index 696185f..4171374 100644
--- a/poisson_matrix.m
+++ b/poisson_matrix.m
@@ -60,6 +60,7 @@ function A = poisson_matrix(integerN, x0, xN)
     A = cat(1, A, u_row);
   end
 
-  ## Finally, append the last row for xN.
-  A = cat(1, A, u_xN_coeffs);
+  ## Finally, append the last row for xN and negate the whole thing (see
+  ## the definition of the poisson problem).
+  A = - cat(1, A, u_xN_coeffs);
 end