Re: Sorting tables by columns

*To*: mathgroup at smc.vnet.net*Subject*: [mg6402] Re: [mg6385] Sorting tables by columns*From*: "w.meeussen" <w.meeussen.vdmcc at vandemoortele.be>*Date*: Sun, 16 Mar 1997 19:25:16 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

At 01:21 15-03-97 -0500, fbd2 at psu.edu wrote: >Hi, > >Does anyone know how to sort tables by one of its columns? >For example, the table > >2 3 4 5 >1 2 7 8 >6 9 2 1 > >can be sorted by column 1, giving: > >1 2 7 8 >2 3 4 5 >6 9 2 1 > >This can be done using Excel; however I need to perform >this operation inside a Mathematica program. >Is there an automated procedure in Mathematica to accomplish this? > >Thanks, > >Flavio > > > hello, as I see it, you are supposed to write them 'on the fly', using tools as found in the help file under 'Sort'. Something along the lines of: In[1]:= it={{2, 3, 4 , 5}, {1 , 2 , 7, 8}, {6 , 9 ,2 , 1}} Out[1]= {{2,3,4,5},{1,2,7,8},{6,9,2,1}} In[2]:= Sort at it Out[2]= {{1,2,7,8},{2,3,4,5},{6,9,2,1}} In[3]:= Sort[it,OrderedQ[{#1[[4]], #2[[4]]}]&] Out[3]= {{6,9,2,1},{2,3,4,5},{1,2,7,8}} In[4]:= Sort[it,#1[[4]]> #2[[4]]&] Out[4]= {{1,2,7,8},{2,3,4,5},{6,9,2,1}} In[5]:= Dimensions[it] Out[5]= {3,4} In[6]:= mytablesort[ m_?MatrixQ, col_Integer/;col<=Dimensions[it][[2]]]:= Sort[m,#1[[col]]> #2[[col]]& ] In[7]:= mytablesort[it,3] Out[7]= {{1,2,7,8},{2,3,4,5},{6,9,2,1}} In[8]:= Remove[mytablesort] extension to 3 and more dimensions get more tricky. bye, Wouter Dr. Wouter L. J. MEEUSSEN eu000949 at pophost.eunet.be w.meeussen.vdmcc at vandemoortele.be