changeset 37:d239bdcdb541

Add fftshift

--- a/blockfuncs.yeti	Sat Dec 22 11:19:46 2012 +0000
+++ b/blockfuncs.yeti	Sun Dec 23 09:21:59 2012 +0000
@@ -21,21 +21,33 @@
     for [0..len-1] do i: v[i] := v1[i] * v2[i] done;
     b.block v);
 
-sqr b =
-    multiply b b;
+sqr bl =
+    multiply bl bl;
+
+rms =
+    sqrt . mean . sqr;
 
 sqrt' =
     b.fromList . (map sqrt) . b.list;
 
-rms =
-    sqrt . mean . sqr;
+fftshift bl =
+   (len = b.length bl;
+    half = int(len/2 + 0.5); // round up for odd-length sequences
+    b.concat [b.rangeOf bl half (len-half), b.rangeOf bl 0 half]);
+
+ifftshift bl =
+   (len = b.length bl;
+    half = int(len/2); // round down for odd-length sequences
+    b.concat [b.rangeOf bl half (len-half), b.rangeOf bl 0 half]);
 
 {
 sum = sum',
 mean,
 multiply, sqr,
 sqrt = sqrt',
-rms
+rms,
+fftshift,
+ifftshift,
 }
 
 

--- a/test/test_blockfuncs.yeti	Sat Dec 22 11:19:46 2012 +0000
+++ b/test/test_blockfuncs.yeti	Sun Dec 23 09:21:59 2012 +0000
@@ -4,7 +4,7 @@
 stdSqrt = sqrt;
 
 { zeros, consts, ones, fromList, list } = load block;
-{ sum, mean, multiply, sqr, sqrt, rms } = load blockfuncs;
+{ sum, mean, multiply, sqr, sqrt, rms, fftshift, ifftshift } = load blockfuncs;
 { declare, compare } = load test.test;
 
 declare [
@@ -46,5 +46,17 @@
         compare ((rms . fromList) [-1,2,2]) (stdSqrt 3)
 ),
 
+"fftshift": \(
+    compare ((list . fftshift . zeros) 0) [] and 
+        compare ((list . fftshift . fromList) [1,2,3,4]) [3,4,1,2] and
+        compare ((list . fftshift . fromList) [1,2,3,4,5]) [4,5,1,2,3]
+),
+
+"ifftshift": \(
+    compare ((list . ifftshift . zeros) 0) [] and 
+        compare ((list . ifftshift . fromList) [3,4,1,2]) [1,2,3,4] and
+        compare ((list . ifftshift . fromList) [4,5,1,2,3]) [1,2,3,4,5]
+),
+
 ];