Re: help with lists operations
- To: mathgroup at smc.vnet.net
- Subject: [mg67846] Re: help with lists operations
- From: "Ray Koopman" <koopman at sfu.ca>
- Date: Mon, 10 Jul 2006 06:38:05 -0400 (EDT)
- References: <e8qgac$o6e$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In the given f1 and f2, all the first numbers in each list
are distinct. If this will always be true then try
Tr[ Split[ Sort@Join[f1,f2], #1[[1]]==#2[[1]]& ] /.
{ {{a_,b_},{a_,c_}}->b*c, {{a_,b_}}->0 }]
omk wrote:
> Hi ALL,
> I am a novice in Mathematica, know that there are no easy ways for learning, so spent 2 weeks trying to solve an easy problem, but so far have only ugly solutions.
> Yes, I read and reread the Book as well as searched for similar problems on the Forum.
> I have 2 lists:
> f1={{2, 1}, {3, 1}, {7, 2}, {9, 1}, {10, 1}, {12, 1}, {14, 3}, {19,
> 3}, {23, 1}, {24, 1}, {25, 1}}
> f2={{2, 2}, {5, 1}, {
> 6, 2}, {10, 1}, {14, 3}, {16, 1}, {18, 1}, {21, 3}, {22, 1}, {26, 1}}
> I need to compare sublists (pairs) from the first list f1 with pairs from f2.
> If pairs with 2 first equal numbers exist, I have to multiply the second, after having products for all such pairs, I need to receive their sum.
> Say from f1 and f2 I have {2,1} and {2,2}, the product is 1 2=2, similar {10,1} and {10,1},{14,3} and {14,3},
> so it should be 2+1+9=12
> Any ideas are very welcome
> TIA,
> omk