diff --git a/mathx.lua b/mathx.lua
index 1f3a51d..fb15dbf 100644
--- a/mathx.lua
+++ b/mathx.lua
@@ -112,7 +112,7 @@ end
 
 --pingpong from 0 to 1 and back again
 function mathx.pingpong(f)
-	return 1 - math.abs(f - 0.5) * 2
+	return 1 - math.abs(1 - f % 2)
 end
 
 --quadratic ease in