Re: Howto sum up a list?
- To: mathgroup at smc.vnet.net
- Subject: [mg106970] Re: [mg106913] Howto sum up a list?
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Fri, 29 Jan 2010 07:50:39 -0500 (EST)
- Reply-to: hanlonr at cox.net
myList = {{eggs, 4}, {milk, 1},
{eggs, 1}, {milk, 1}};
{#[[1, 1]], Total[#[[All, 2]]]} & /@
GatherBy[myList, First]
{{eggs, 5}, {milk, 2}}
{#, Total[Cases[myList, {#, n_} :> n]]} & /@
Union[myList[[All, 1]]]
{{eggs, 5}, {milk, 2}}
myList //.
{s___, {t_, j_}, m___, {t_, k_},
e___} :>
{s, {t, j + k}, m, e}
{{eggs, 5}, {milk, 2}}
Bob Hanlon
---- Jonas Stein <news at jonasstein.de> wrote:
=============
How can i sum up the list:
MyList = {{eggs, 4}, {milk, 1}, {eggs, 1}, {milk, 1}}
I want to get something like:
{{eggs, 5},{milk, 2}}
I tyied Tally[], but that ignored the factor 4 in {eggs, 4}
Thank you.
--
Jonas Stein <news at jonasstein.de>