Message-ID: <DovoiFAQo0e8Ew7t@myatt.demon.co.uk>
Date: 2002-02-26T08:40:48Z
From: Mark Myatt
Subject: another basic ?
In-Reply-To: <4.3.2.7.2.20020225120152.00a9d100@pop.service.ohio-state.edu>
jimi adams <adams.644 at osu.edu> writes:
>i am sure that there is a simple solution that i am just overlooking, but
>there is no logical test for =
>there is one for != and >,<, >=, <=...
>what do i do if i need to check if something IS EQUAL
==
> or is there an easy way, in working with a matrix of size n x 3, to sort
> the matrix by one of the columns?
Use order() with the column (or row) indices:
my.matrix[order(my.matrix[,column.to.sort.on]), ]
As in:
> my.matrix <- matrix(c(5:1, 6:8, 12:9), nrow = 4)
> my.matrix
[,1] [,2] [,3]
[1,] 5 1 12
[2,] 4 6 11
[3,] 3 7 10
[4,] 2 8 9
> my.sorted.matrix <- my.matrix[order(my.matrix[ ,1]), ]
> my.sorted.matrix
[,1] [,2] [,3]
[1,] 2 8 9
[2,] 3 7 10
[3,] 4 6 11
[4,] 5 1 12
Best wishes,
Mark
--
Mark Myatt
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