我有一个长格式的数据框,其中有两个因子变量作为列,第一列代表一系列唯一的类,第二列代表分组变量(在本例中为类(class)发生的城市)。
class <- c("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K")
city <- c("Atlanta", "Atlanta", "Atlanta", "Detroit", "Detroit", "Milwaukee", "Milwaukee", "Milwaukee", "Milwaukee", "Portland", "Juneau")
samp <- data.frame(class, city)
samp
# class city
# A Atlanta
# B Atlanta
# C Atlanta
# D Detroit
# E Detroit
# F Milwaukee
# G Milwaukee
# H Milwaukee
# I Milwaukee
# J Portland
# K Juneau
对于每个城市,我想要一份在那里举办的所有类(class)的列表。理想情况下,输出如下所示:
class.list <- list(Atlanta = c("A", "B", "C"), Detroit = c("D", "E"), Milwaukee = c("F", "G", "H", "I"), Portland = "J", Juneau = "K")
class.list
# $Atlanta
# [1] "A" "B" "C"
#
# $Detroit
# [1] "D" "E"
#
# $Milwaukee
# [1] "F" "G" "H" "I"
#
# $Portland
# [1] "J"
#
# $Juneau
# [1] "K"
我尝试过各种解决方案,但都失败了。可以说,我最接近的是通过 dcast
,但这并不是我想要的输出:
library(reshape2)
class.list <-dcast(samp, city ~ class)
class.list
# place A B C D E F ...
# Atlanta Atlanta Atlanta Atlanta <NA> <NA> <NA> ...
# Detroit <NA> <NA> <NA> Detroit Detroit <NA> ...
# ...
最佳答案
我们可以使用split
split(as.character(samp$class), samp$city)
#$Atlanta
#[1] "A" "B" "C"
#$Detroit
#[1] "D" "E"
#$Juneau
#[1] "K"
#$Milwaukee
#[1] "F" "G" "H" "I"
#$Portland
#[1] "J"
或者另一个选项是unstack
unstack(samp, class~city)
关于r - 从一列中提取另一列中的每个组的列表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35273433/