问题
Say I have some data created like this
n <- 3
K <- 4
dat <- expand.grid(var1=1:n, var2=1:K)
dat looks like this:
var1 var2
1 1 1
2 2 1
3 3 1
4 1 2
5 2 2
6 3 2
7 1 3
8 2 3
9 3 3
10 1 4
11 2 4
12 3 4
I want to remove some rows from both data frames in the list at the same time. Let's say I want to remove the 11th row, and I want the 'gap' to be filled in, so that now the 12th row will become the 11th row.
I understand this is a list of two data frames. Thus the advice here does not apply, since dat[[11]]<-NULL would do nothing, while dat[[2]]<-NULL would remove the second data frame from the list
lapply(dat,"[",11) lets me access the relevant elements, but I don't know how to remove them.
回答1:
Assuming that we want to remove rows from a list of data.frames, we loop the list elements using lapply and remove the rows using numeric index.
lapply(lst, function(x) x[-11,])
Or without the anonymous function
lapply(lst, `[`, -11,)
The 'dat' is a data.frame.
is.data.frame(dat)
#[1] TRUE
If we want to remove rows from 'dat',
dat[-11,]
If the row.names also needs to be changed
`row.names<-`(dat[-11,], NULL)
data
lst <- list(dat, dat)
来源：https://stackoverflow.com/questions/33185456/r-how-can-i-remove-rows-from-all-the-data-frames-in-this-list