r - 使用自定义中断来剪切日期向量

Question

我想根据定义的休息(0-7天，8-15天，...，31-50天)来削减日期范围，然后计算组平均值值(value)。

library(dplyr)

date = seq(as.Date("2019/1/1"), by = "day", length.out = 50)
value = matrix(rnorm(200, 100, 50), nrow=50) %>% data.frame()
sample = cbind(date, value) %>% data.frame()

breaks = c(0, 7, 15, 30, 50)

sample %>%
  group_by(cutt = cut(StayDate, breaks=breaks)) %>%
  summarise(m1 = mean(X1), m2=mean(X2))

不过，cut函数似乎只能使用“日”、“周”等来进行剪切。我有什么办法可以做到吗？

Answer 1

我们可以转换为“factor”，然后再转换回“numeric”。

library(dplyr)
sample %>%
  group_by(cutt=cut(as.numeric(factor(date)), breaks=breaks)) %>%
  summarise(m1=mean(X1), m2=mean(X2))
# # A tibble: 4 x 3
# cutt       m1    m2
# <fct>   <dbl> <dbl>
# 1 (0,7]   126.  120. 
# 2 (7,15]  123.   90.3
# 3 (15,30]  82.6 107. 
# 4 (30,50]  90.4 104. 

或者以 R 为基数:

do.call(rbind, by(sample[2:3], cut(as.numeric(factor(sample$date)), breaks), colMeans))
#                X1        X2
# (0,7]   125.79941 120.01652
# (7,15]  122.82247  90.33681
# (15,30]  82.64698 107.13250
# (30,50]  90.39701 104.09779

数据

set.seed(42)
n <- 50
sample <- data.frame(date=seq(as.Date("2019/1/1"), by="day", length.out=n),
                  matrix(rnorm(4*n, 100, 50), ncol=4, 
                         dimnames=list(NULL, paste0("X", 1:4))))
breaks <- c(0, 7, 15, 30, 50)