将所有因子级别的名称作为新列从三列data.table [R] [英] Return all factor levels by name as new columns from a three column data.table [R]
本文介绍了将所有因子级别的名称作为新列从三列data.table [R]的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
library(data.table)
(DT = data.table(a = LETTERS [c(1,3,8)],b = c(2,4:7),
c = as.factor(c bob,mary,bob,george,alice)),key =a))
返回:
#abc
#1:A 2 bob
#2:A 4 mary
#3:B 5 bob
#4:C 6 george
#5:H 7 alice
想要得到这个:
#alice bob george mary
#1:A NA 2 NA NA
#2:A NA NA NA 4
#3:B NA 5 NA NA
#4:C NA NA 6 NA
#5:H 7 NA NA NA
解决方案
类似于创建虚拟变量。
uc< - sort(unique(as.character(DT $ c)))
DT [,(uc):= lapply(uc,function(x)ifelse(c == x,b,NA))] [,c('b','c'):= NULL]
我听说过有关 ifelse
,所以更快的路线可能是
uc< - sort(unique(as.character(DT $ c)))
是< - 1:nrow(DT)
js< - as.character(DT $ c)
vs < - DT
$ b $对于(i in)set(DT,i = is [i],j = js [i],value = vs [i])
$ [$(uc):= NA_integer_]
$ b DT [,c('b','c'):= NULL]
Any way to use data.table or dplyr to solve the below?
library(data.table)
(DT = data.table(a = LETTERS[c(1, 1:3, 8)], b = c(2, 4:7),
c = as.factor(c("bob", "mary", "bob", "george", "alice")), key="a"))
Returns:
# a b c
# 1: A 2 bob
# 2: A 4 mary
# 3: B 5 bob
# 4: C 6 george
# 5: H 7 alice
Would like to get this:
# alice bob george mary
# 1: A NA 2 NA NA
# 2: A NA NA NA 4
# 3: B NA 5 NA NA
# 4: C NA NA 6 NA
# 5: H 7 NA NA NA
解决方案
This is similar to creating dummy variables.
uc <- sort(unique(as.character(DT$c)))
DT[,(uc):=lapply(uc,function(x)ifelse(c==x,b,NA))][,c('b','c'):=NULL]
I've heard bad things about ifelse
, so a speedier route may be
uc <- sort(unique(as.character(DT$c)))
is <- 1:nrow(DT)
js <- as.character(DT$c)
vs <- DT$b
DT[,(uc):=NA_integer_]
for (i in is) set(DT,i=is[i],j=js[i],value=vs[i])
DT[,c('b','c'):=NULL]
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