Re: Something very simple.....
- To: mathgroup at smc.vnet.net
- Subject: [mg87124] Re: Something very simple.....
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Tue, 1 Apr 2008 05:41:31 -0500 (EST)
- Organization: The Open University, Milton Keynes, UK
- References: <fssr6s$biu$1@smc.vnet.net>
Steve Gray wrote:
<snip>
> 2. I have two lists, lsta={a,b,c,d,e,f} and lstb={1,3,4}.
> I want the elements of lsta that do NOT correspond to elements
> of lstb, in this case everything from lsta except elements
> 1,3, and 4: result={b,e,f}.
> (lstb won't have entries larger than Length[lsta]).
The following will do it:
Pick[lsta,
If[MemberQ[lstb, #], False, True] & /@ Range@Length@lsta]
Here is how it works:
lsta = {a, b, c, d, e, f} ; lstb = {1, 3, 4};
(* We build a list of same length as lsta since Pick expects two list of
same length. *)
Range@Length@lsta
{1, 2, 3, 4, 5, 6}
(* We mark what elements must be taken. *)
If[MemberQ[lstb, #], False, True] & /@ Range@Length@lsta
{False, True, False, False, True, True}
(* The final expression is *)
Pick[lsta,
If[MemberQ[lstb, #], False, True] & /@ Range@Length@lsta]
{b, e, f}
Regards,
-- Jean-Marc