MathGroup Archive 2001

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: sort


In a message dated 2001/7/20 3:36:01 AM, nails at asu.edu writes:

>Does anybody now how to sort a matrix first by one column and then by
>another column (giving priority to the first column and sorting by
>second column only when there are ties in the first column).
>

sortByCol[l_List, n_Integer] := 
    Sort[l, #1[[n]] <= #2[[n]]&];

mat = Table[Random[Integer, {1, 4}], {10}, {10}];

sortByCol[mat, 3]

To sort by column 3 with column 4 breaking ties

sortByCol[sortByCol[mat, 4], 3]

If more than two columns are to be used 

Fold[sortByCol[#1, #2]&, mat, {5, 4, 3}]


Bob Hanlon
Chantilly, VA  USA


  • Prev by Date: Re: Integrate[Sqrt[Tan[x]], {x, 0, 1}] -- approx ??
  • Next by Date: Re: Integrate[Sqrt[Tan[x]], x]
  • Previous by thread: Re: sort
  • Next by thread: Re: sort