Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2006
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Lists of all values of a two-variable function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg64751] Re: [mg64735] Lists of all values of a two-variable function
  • From: "Igor C. Antonio" <igora at wolf-ram.com>
  • Date: Thu, 2 Mar 2006 06:47:39 -0500 (EST)
  • Organization: Wolfram Research, Inc.
  • References: <200603011104.GAA23021@smc.vnet.net>
  • Reply-to: igora at wolf-ram.com
  • Sender: owner-wri-mathgroup at wolfram.com

José Carlos Santos wrote:
> Hi all,
> 
> I would like to do this: given a function _f_ in two variables and two
> lists l1 and l2, to get the list of all values f[a,b] with _a_ in l1 and
> _b_ in l2, with all duplicated values removed. How do I do that?
> 
> The closest thing that I am able to do is:
> 
> Table[f[l1[[i]],l2[[j]]],{i,1,Length[l1]},{j,1,Length[l2]}]
> 
> but, of course:
> 
> 1) what I get is a list of lists;
> 
> 2) I eventually get duplicated values.
> 
> Best regards,
> 
> Jose Carlos Santos

l1 = {1,1,2}; l2 = {1,2,3};

This code is more simple than the the second (further below), but the duplicates 
are removed only f has been evaluated:

In[30]:=
Union[Flatten[Outer[f[##]&,l1,l2],1]]

Out[30]=
{f[1,1],f[1,2],f[1,3],f[2,1],f[2,2],f[2,3]}

The alternative is to calculate all possible arguments of f, remove the 
duplicates, then map f over the results:

In[33]:=
f[Sequence@@#]& /@ Union[Flatten[Outer[List,l1,l2],1]]

Out[33]=
{f[1,1],f[1,2],f[1,3],f[2,1],f[2,2],f[2,3]}

Very similar code, but if your f has a long running-time, the second choice is 
better.

--
Igor C. Antonio
Wolfram Research, Inc.
http://www.wolfram.com

To email me personally, remove the dash.


  • Prev by Date: Re: Nonlinear Fit of Complex functions
  • Next by Date: Re: Derivation of Sums of Functions
  • Previous by thread: Re: Lists of all values of a two-variable function
  • Next by thread: Re: Lists of all values of a two-variable function