Re: Howto sum up a list?
- To: mathgroup at smc.vnet.net
- Subject: [mg107067] Re: Howto sum up a list?
- From: stejaes <sjaeschke at gmail.com>
- Date: Tue, 2 Feb 2010 03:26:03 -0500 (EST)
- References: <hjrf6g$mur$1@smc.vnet.net>
On Jan 28, 8:43 am, Jonas Stein <n... 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 <n... at jonasstein.de> This solution is great and straight forward: {#[[1, 1]], Total[#[[ All, 2]]]} & /@ Split[Sort[MyList], StringMatchQ[ToString[First[#1]], \ ToString[First[#2]]] &]