Re: Custom sort a list of pairs
- To: mathgroup at smc.vnet.net
- Subject: [mg73698] Re: Custom sort a list of pairs
- From: Bill Rowe <readnewsciv at sbcglobal.net>
- Date: Sat, 24 Feb 2007 02:32:51 -0500 (EST)
On 2/23/07 at 4:41 AM, planetmarshalluk at hotmail.com wrote: >For example, I want some function >sortPairs[items_] >that when given the input >{{ 1,a},{2,a},{3,a},{1,b},{2,b},{1,c}} >produces the output >{{3,a},{2,a},{2,b}{1,a},{1,b},{1,c}} Here is one way to do what you want In[10]:= data={{1,a},{2,a},{3,a},{1,b},{2,b},{1,c}}; In[11]:= Join@@(Reverse[Sort@#]&/@ Split[Sort[data, OrderedQ@{Last@#1, Last@#2}&], Last@#1 == Last@#2&]) Out[11]= {{3, a}, {2, a}, {1, a}, {2, b}, {1, b}, {1, c}} -- To reply via email subtract one hundred and four