[R] another basic ?

[Mark Myatt]

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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