[英]Filling in values in a data frame in R?
假設我有這個數據框:
times vals
1 1 2
2 3 4
3 7 6
設置
foo <- data.frame(times=c(1,3,7), vals=c(2,4,6))
我想要這個:
times vals
1 1 2
2 2 2
3 3 4
4 4 4
5 5 4
6 6 4
7 7 6
也就是說,我希望從1到7填寫所有時間,並填寫不超過給定時間的最新時間的val。
我有一些代碼使用dplyr來做,但它很難看。 建議更好?
library(dplyr)
foo <- merge(foo, data.frame(times=1:max(foo$times)), all.y=TRUE)
foo2 <- merge(foo, foo, by=c(), suffixes=c('', '.1'))
foo2 <- foo2 %>% filter(is.na(vals) & !is.na(vals.1) & times.1 <= times) %>%
group_by(times) %>% arrange(-times.1) %>% mutate(rn = row_number()) %>%
filter(rn == 1) %>%
mutate(vals = vals.1,
rn = NULL,
vals.1 = NULL,
times.1 = NULL)
foo <- merge(foo, foo2, by=c('times'), all.x=TRUE, suffixes=c('', '.2'))
foo <- mutate(foo,
vals = ifelse(is.na(vals), vals.2, vals),
vals.2 = NULL)
這是標准的滾動連接問題:
library(data.table)
setDT(foo)[.(1:7), on = 'times', roll = T]
# times vals
#1: 1 2
#2: 2 2
#3: 3 4
#4: 4 4
#5: 5 4
#6: 6 4
#7: 7 6
以上是devel版本(1.9.7+),它更適合連接期間的列匹配。 對於1.9.6,您仍需要為內部表指定列名:
setDT(foo)[.(times = 1:7), on = 'times', roll = T]
approx
:
data.frame(times = 1:7,
vals = unlist(approx(foo, xout = 1:7, method = "constant", f = 0)[2], use.names = F))
times vals
1 1 2
2 2 2
3 3 4
4 4 4
5 5 4
6 6 4
7 7 6
dplyr
和tidyr
選項:
library(dplyr)
library(tidyr)
foo %>%
right_join(data_frame(times = min(foo$times):max(foo$times))) %>%
fill(vals)
# Joining by: "times"
# times vals
# 1 1 2
# 2 2 2
# 3 3 4
# 4 4 4
# 5 5 4
# 6 6 4
# 7 7 6
這是一個更長,更冗長的基礎R解決方案:
# calculate the number of repetitions needed for vals variable
reps <- c(with(foo, times[2:length(times)]-times[1:length(times)-1]), 1)
# get result
fooDoneIt <- data.frame(times = min(foo$times):max(foo$times),
vals = rep(foo$vals, reps))
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