[R] how to get row name of matrix when result is a vector

syrvn mentor_ at gmx.net
Fri Sep 3 15:08:30 CEST 2010


Hi,

the R code:

a <- matrix(c(1,5,4,3,7,10,34,4,3,8,6,5,12,17,45,3,2,45,46,47,3,4,22,12,21),
nrow=5)
rownames(a) <- c("a","b","c","d","e")
a
a[which(a[,3] < 8), ]
a[which(a[,3] < 6), ]


produces the following output:

> a
  [,1] [,2] [,3] [,4] [,5]
a    1   10    6    3    3
b    5   34    5    2    4
c    4    4   12   45   22
d    3    3   17   46   12
e    7    8   45   47   21

> a[which(a[,3] < 8), ]
  [,1] [,2] [,3] [,4] [,5]
a    1   10    6    3    3
b    5   34    5    2    4

> a[which(a[,3] < 6), ]
[1]  5 34  5  2  4


I actually thought it must be rather easy to somehow extract the row name
when the result is just a vector as in the second example and not a matrix.
I tried several ways but without any success.

Any advice?
Best,
syrvn 


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