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>
- newbie question on sorting