[英]Accessing elements in list in r
我想訪問列表中的某個元素,並將其存儲在data.frame中。 如果特定對象沒有該元素,則結果應為NA。
例:
list
$A
"mark" "peter" "sam" "il"
$B
"dd" "pp" "tt" "ff" "jj" "rr"
$C
"aa" "aa" "aa" "aa" "aa" "aa"
通過調用整個列表中的第六個元素的結果應該是:
結果(數據。框架):
name value
<NA> A
rr B
aa C
有什么建議嗎?
您可以使用sapply
和data.frame
:
# The list
l <- list(A = c("mark", "peter", "sam", "il"),
B = c("dd", "pp", "tt", "ff", "jj", "rr"),
C = c("aa", "aa", "aa", "aa", "aa", "aa"))
# extract sixth element in each vector
res <- sapply(l, "[", 6)
# combine to data frame
dat <- data.frame(name = res, value = names(res))
# name value
# A <NA> A
# B rr B
# C aa C
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