Displaying 3 results from an estimated 3 matches for "colidx".
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colid
2004 Jul 08
2
Getting elements of a matrix by a vector of column indice s
See if the following helps:
> m <- outer(letters[1:5], 1:4, paste, sep="")
> m
[,1] [,2] [,3] [,4]
[1,] "a1" "a2" "a3" "a4"
[2,] "b1" "b2" "b3" "b4"
[3,] "c1" "c2" "c3" "c4"
[4,] "d1" "d2" "d3" "d4"
[5,]
2012 Dec 12
2
using 'apply' to apply princomp to an array of datasets
Hi everyone,
Suppose I have a 3D array of datasets, where say dimension 1 corresponds to
cases, dimension 2 to datasets, and dimension 3 to observations within a
dataset. As an example, suppose I do the following:
> x <- sample(1:20, 48, replace=TRUE)
> datasets <- array(x, dim=c(4,3,2))
Here, for each j=1,2,3, I'd like to think of datasets[,j,] as a single data
matrix with
2003 Oct 27
2
how to select random rows ?
How can I select random subsets (rows!) from a data set ?
If I generate simple data set
> a <- data.frame(x=1:2, y = NaN, z = 2:1)
> a
x y z
1 1 NaN 2
2 2 NaN 1
I can select random subsets (colums) very easily using sample function:
> sample(a, 2)
z y
1 2 NaN
2 1 NaN
I expected that using transpose of a would do the same for rows, but I am
getting
rather unexpected