Re: newbie question on sorting

*To*: mathgroup at smc.vnet.net*Subject*: [mg26446] Re: [mg26420] newbie question on sorting*From*: Ken Levasseur <Kenneth_Levasseur at uml.edu>*Date*: Thu, 21 Dec 2000 01:51:47 -0500 (EST)*References*: <200012200521.AAA05601@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

niels: Sort will automatically sort according to the first column since the standard lexicographic ordering of the rows would start there. For example, if you start with this simple example: In[1]:= M = Table[Random[Integer, {0, 100}], {4}, {4}] Out[1]= {{23, 86, 53, 4}, {43, 24, 66, 23}, {98, 44, 33, 33}, {90, 50, 58, 14}} You can see that the sorting is done as you desire. In[2]:= Sort[M] Out[2]= {{23, 86, 53, 4}, {43, 24, 66, 23}, {90, 50, 58, 14}, {98, 44, 33, 33}} What's probably less obvious is how you would sort by some other column. To do that you can add a second argument to Sort which is a pure function of two variable. In[3]:= Sort[M, #1[[2]] <= #2[[2]] & ] Out[3]= {{43, 24, 66, 23}, {98, 44, 33, 33}, {90, 50, 58, 14}, {23, 86, 53, 4}} Ken Levasseur Mathematical Sciences UMass Lowell Three credit on-line Introduction to Mathematica starts at the end of January: http://faculty.uml.edu/klevasseur/courses/m419/m419.html niels Waller wrote: > Dear mathgroup readers, > > I have just started using Mathematica for a programming task and have run > into a difficulty. I have a matrix M. I would like to sort the rows of M > based on the values of the first column. Is there any easy way to do this? > Any and all help will be greatly appreciated. > > Thanks, > > Niels > > Please send suggestions to: niels.waller at vanderbilt.edu > > ******************************************************* > Niels Waller, Ph.D. > Director of Quantitative Methods and Evaluation > Department of Psychology and Human Development > Vanderbilt University > Phone: (615) 322-8380 email: niels.waller at vanderbilt.edu > QME Home page: http://www.vanderbilt.edu/quantmetheval/ > *******************************************************

**References**:**newbie question on sorting***From:*"niels Waller" <niels.waller@home.com>