diff general/discretise/intmap.m @ 4:e44f49929e56

Adding reorganised general toolbox, now in several subdirectories.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/general/discretise/intmap.m	Sat Jan 12 19:21:22 2013 +0000
@@ -0,0 +1,26 @@
+function M=intmap(min,max)
+% intmap - Discretisation map for integers (ie alread discrete)
+%
+% intmap :: integer~'min value', integer~'max value' -> dmap(N).
+%
+% Maps integers to natural numbers, saves on multiplications and
+% roundings as performed by the real->natural maps.
+
+	N=max-min+1;
+	off=min-1;
+	M=dmap(N,@map,@revmap);
+
+	function I=map(X)
+		I=X-off;
+		I(I<1)=-inf;
+		I(I>N)=inf;
+	end
+
+	function X=revmap(I)
+		I=shiftdim(shiftdim(I),-1);
+		X1=off+I-0.5;
+		X2=off+I+0.5;
+		X=cat(1,X1,X2);
+	end
+end
+