updated documentation

thanks, @aelocson

editions/tw5.com/tiddlers/filters/getindex.tid

@@ -3,15 +3,15 @@ modified: 20150203140000000
 tags: [[Filter Operators]] [[Field Operators]]
 title: getindex Operator
 caption: getindex
-purpose: returns the value at an index of DataTiddlers
+purpose: select all values of a data property in the input titles
 
 <$macrocall $name=".operator-def"
 input="a [[selection of titles|Title Selection]]"
-parameter="the name of an [[index|DataTiddlers]]"
-paramName="i"
-output="the values at index <<.place f>> in each of the input titles"
+parameter="the name of a [[property|DataTiddlers]]"
+paramName="P"
+output="the values of property <<.place P>> in each of the input titles"
 />
 
-Each input title is tested in turn. If the corresponding tiddler is a [[DataTiddler|DataTiddlers]] and has the index <<.place i>> defined, its value is appended to the output.
+Each input title is processed in turn, and is ignored if it does not denote a [[data tiddler|DataTiddlers]]. If the tiddler contains property <<.place P>>, the value of that property is [[dominantly appended|Dominant Append]] to the output.
 
 <<.operator-examples "getindex">>