diff --git a/D3.md b/D3.md
index f2ebbbc..8cae0b9 100644
--- a/D3.md
+++ b/D3.md
@@ -74,7 +74,7 @@ d3.selectAll('circle')//make a "ghost call" to all circles, even if there are no
 once data has been bound to elements, you can call something like:
 
 ```javascript
-selection.attr('r', function(d,i){ //d is data for the current element, i is the index of that element in the array
+d3.selectAll('circle').attr('r', function(d,i){ //d is data for the current element, i is the index of that element in the array
 	//callback will be executed for each DOM element
 	//return value is how each value will be set
 	return d.value * 2 //takes value property of d (data), multiplies it by two and sets the radius to that