diff util/classes/@dictionary/spark.m @ 160:e3035d45d014 danieleb

Added support classes

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/util/classes/@dictionary/spark.m	Wed Aug 31 10:53:10 2011 +0100
@@ -0,0 +1,35 @@
+function varargout = Spark(obj)
+% Calculates the minimum number of linearly dependent atoms in the matrix A
+% WARNING: this function computes a combinatorial function, use only if the
+% size of the problem is small (i.e. <20)
+if nargout <= 1
+    A = obj.phi;
+    k = size(A,2);
+    if k>20
+        warning('This function computes a combinatorial function, use only if thesize of the problem is small (i.e. <20).');
+        choice = input('The calculation of spark will take a long time... do you wish to continue anyway (y/n)','s');
+        if strcmpi( choice,'n')
+            return
+        end
+    end
+    sigma = 2;
+    while true
+        P = nchoosek(1:k,sigma);
+        for i=1:size(P,1)
+            r = rank(A(:,P(i,:)));
+            if r<sigma
+                varargout{1} = sigma;
+                return
+            end
+        end
+        sigma = sigma + 1;
+        if sigma==k
+            varargout{1} = inf;
+            return
+        end
+    end
+else
+    %% TODO: calculate lower and upper bounds on the spark
+    varargout{1} = 2;
+    varargout{2} = inf;
+end