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