如何通过选择列表中除一个值之外的所有元素来对R中的列表进行子集化？

Question

So basically I have a list called "parameters" with values (x1, x2, ... , xj). I want to, through a for loop, subset this list, but each time leave out one element. So for example I want the first subset (through the first iteration of the for loop) to be (x2, x3, ..., xj), and the next to be (x1, x3, ..., xj) and so on, until the last subset which would be (x1, x2, ... , xj-1). How do I do this?

Answer 1

this could be useful

> Vector <- paste("x", 1:6, sep="")
> lapply(1:length(Vector), function(i) Vector[-i])

Answer 2

I'm assuming by "list" you mean vector . If so:

parameters <- rnorm(100)
y <- matrix(nrow=length(parameters)-1,ncol=length(parameters))
for(i in 1:length(parameters))
    y[,i] <- parameters[-i]

If by "list", you actually mean a list , the code is basically the same, but just do parameters <- unlist(parameters) first.

Answer 3

You can subset the element from the list by indicating they order in the list.

To select the items 1 and 3 from a list

my.list[c(1,3))]

Try this:

# create a dummy list of data frames
d1 <- data.frame(y1=c(1,2,3),y2=c(4,5,6))
d2 <- data.frame(y1=c(3,2,1),y2=c(6,5,4))
d3 <- data.frame(y1=c(3,2,1),y2=c(9,8,7))
my.list <- list(d1, d2, d3)

# get the items 1 and 3
my.list[c(1,3)]

# get the all element except of the first one
my.list[c(-1)]

Answer 4

Just in case you want to use the data for a leave-one-out jackknife, here a quick pointer to the bootstrap package and a short example

library(bootstrap)
vec_list=list()
jackknife(rnorm(10,0,1),function(x) {vec_list[[length(vec_list)+1]]<<-x;mean(x)})
vec_list[1:10]