From: Michael Orlitzky <michael@orlitzky.com>
Date: Sun, 5 May 2013 01:12:09 +0000 (-0400)
Subject: Fix existing rank_k_approximation() tests; add new ones.
X-Git-Url: http://gitweb.michael.orlitzky.com/?p=octave.git;a=commitdiff_plain;h=4684857f18bb97f9b6ed8b4bf4622fd1d82dfcb5;hp=b39f6d3f6aaaebe891c09a8923547f25c2d43b84

Fix existing rank_k_approximation() tests; add new ones.
---

diff --git a/tests/rank_k_approximation_tests.m b/tests/rank_k_approximation_tests.m
index 8288752..f1339b6 100644
--- a/tests/rank_k_approximation_tests.m
+++ b/tests/rank_k_approximation_tests.m
@@ -1,20 +1,48 @@
-U = [4/5, 3/5, 0  ; ...
-     0  , 4/5, 3/5; ...
-     3/5, 0  , 4/5 ];
+U = [ 0, 0, 1; ...
+      0, 1, 0; ...
+      1, 0, 0 ];
 
-S = [ 1, 0, 0;
-      0, 2, 0;
-      0, 0, 3 ];
+S = [ 3, 0, 0; ...
+      0, 2, 0; ...
+      0, 0, 1 ];
 
-V = [ 0, 1, 0;
-      1, 0, 0;
+V = [ 0, 1, 0; ...
+      1, 0, 0; ...
       0, 0, 1 ];
 
 A = U*S*V';
 
 expected = A;
+% This should be exact.
 actual = rank_k_approximation(A, 3);
 
 unit_test_equals("Full rank approximation of a matrix is itself", ...
-		 expected, ...
-		 actual);
+		 actual, ...
+		 expected);
+
+
+
+% This too.
+actual = rank_k_approximation(A, 13);
+
+unit_test_equals("Full rank approximation of a matrix is itself", ...
+		 actual, ...
+		 expected);
+
+
+S2 = S;
+S2(3,3) = 0;
+expected = U*S2*V';
+actual = rank_k_approximation(A, 2);
+unit_test_equals("Rank 2 approximation of a matrix is correct", ...
+		 true, ...
+		 (norm(actual - expected) <= 1e-10));
+
+
+S1 = S2;
+S1(2,2) = 0;
+expected = U*S1*V';
+actual = rank_k_approximation(A, 1);
+unit_test_equals("Rank 1 approximation of a matrix is correct", ...
+		 true, ...
+		 (norm(actual - expected) <= 1e-10));