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Re: A little help with sort

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  • Subject: [mg112520] Re: A little help with sort
  • From: Bob Hanlon <hanlonr at>
  • Date: Sat, 18 Sep 2010 07:26:13 -0400 (EDT)

data = RandomInteger[4, {25, 5}];

(sort1 = SortBy[Reverse[SortBy[data, #[[4]] &]],
    {#[[1]] &, #[[2]] &}]) // Grid

When column 4 is all numeric, then

(sort2 = SortBy[data,
    {#[[1]] &, #[[2]] &, -#[[4]] &}]) // Grid

Bob Hanlon

---- "Blackwell wrote: 

The problem I am having:

Let's  say I have a 200 x 200 matrix.

I want to sort it in order of the values in column one.

Then I want it to sort all the doubles by the values in column two.

Then I want it to sort all the double doubles by reverse of the values
of column 4 or whatever. 

Is there an easy way to do this. I know I can write something long and
annoying to do it, but I'm getting to the point in my use of mathematica
where I want to write more concise code.

Sort[Matrix, #1[[1]]>#2[[1]]&] seems to totally negate any pre
sorting... I tried to fold it backwards starting from column 4 and it
seems that sort just ignores whatever I do then.

Thanks in advance,


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