r - 按矢量日期定义的周分组的事件

Question

我想计算在由日期向量定义的每个时期内发生的所有事件。矢量表示每个时期的第一天。结果应该是一个与输入向量长度相同且出现次数相同的向量。

我提出了一个效率极低的“循环”解决方案(见下文)。我想知道是否有任何方法可以更快地处理相同的任务。

events <- c("2000-01-05", "2000-02-08", "2000-04-09", "2000-02-08", "2000-03-13", "2000-03-13")

# Create vector of dates (in this case 52, 7 days periods)
week_vector = as.Date("2000-01-01")
i <- 1; N <- 51
while (i <= N) {
week_vector = append(week_vector, as.Date(week_vector[i] + 7)) 
  i <- i + 1
}

i <- 1; N <- length(week_vector)
while (i <= N) {
  occurrences_by_week <- sum(events >= week_vector[i] & events < week_vector[i] + 7)
}

我最初想出了这个解决方案(使用 zoo 包的 rollapply)。但是使用 rollapply 我无法定义我希望开始对事件进行分组的日期:

frequency <- as.data.frame(table(as.Date(events)))

frequency.zoo <- read.zoo(frequency)

frequency.zoo.week <- rollapply(frequency.zoo, 7, sum, by = 7)

Answer 1

是这样的吗？

events <- as.Date(c("2000-01-05", "2000-02-08", "2000-04-09", "2000-02-08",
            "2000-03-13", "2000-03-13"))

week_vector <- seq(from = as.Date("2000-01-01"), to = as.Date("2000-12-23"), by = 7)
# or arguments more similar to the wording in the question, "52 [dates], 7 days periods":
week_vector <- seq(from = as.Date("2000-01-01"), length.out = 52, by = 7)

events2 <- cut(events, breaks = week_vector)

table(events2)

# 2000-01-01 2000-01-08 2000-01-15 2000-01-22 2000-01-29 2000-02-05 2000-02-12 2000-02-19 
# 1          0          0          0          0          2          0          0 
# 2000-02-26 2000-03-04 2000-03-11 2000-03-18 2000-03-25 2000-04-01 2000-04-08 2000-04-15 
# 0          0          2          0          0          0          1          0 
# 2000-04-22 2000-04-29 2000-05-06 2000-05-13 2000-05-20 2000-05-27 2000-06-03 2000-06-10 
# 0          0          0          0          0          0          0          0 
# 2000-06-17 2000-06-24 2000-07-01 2000-07-08 2000-07-15 2000-07-22 2000-07-29 2000-08-05 
# 0          0          0          0          0          0          0          0 
# 2000-08-12 2000-08-19 2000-08-26 2000-09-02 2000-09-09 2000-09-16 2000-09-23 2000-09-30 
# 0          0          0          0          0          0          0          0 
# 2000-10-07 2000-10-14 2000-10-21 2000-10-28 2000-11-04 2000-11-11 2000-11-18 2000-11-25 
# 0          0          0          0          0          0          0          0 
# 2000-12-02 2000-12-09 2000-12-16 
# 0          0          0