Re: List operations
- To: mathgroup at smc.vnet.net
- Subject: [mg25447] Re: List operations
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sun, 1 Oct 2000 02:44:29 -0400 (EDT)
- References: <8r196t$hs8@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Mat,
Two ideas:
Cases[data, {x_, y_} /; 3x + y^2 == 7]
{{1, 2}, {2, 1}}
op[{x_, y_}] := 3x + y^2
Select[data, op[#] == 7 &]
{{1, 2}, {2, 1}}
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"Matt Herman" <Henayni at hotmail.com> wrote in message
news:8r196t$hs8 at smc.vnet.net...
>
> Hi,
>
> Suppose I have a list of ordered pairs {{a1,b1},{a2,b2},...,{an,bn}}.
> What is an efficient way of pulling out all the pairs such that, if I do
> an operation on the first element in the list, and another on the
> second, and I sum them, they equal some predetermined constant?
>
> For instance, say 3*listpart[[1]]+listpart[[2]]^2
>
> Thanks
>
>