R中的嵌套循环以计算平均天数

首先，我们创建一个数据框对象，以便我们可以轻松地操作数据：

df <- read.csv(stringsAsFactors = TRUE, text = 'date, temp, Hour, DayCount
01/01/17, -2, 0 , 1
01/01/17, -2, 1 , 1
01/01/17, -2, 2 , 1
01/01/17, -3, 3 , 1
01/01/17, -4, 4 , 1
01/01/17, -4, 5 , 1
01/01/17, -5, 6 , 1
01/01/17, -6, 7 , 1
01/01/17, -4, 8 , 1
01/01/17, -2, 9 , 1
01/01/17, -1, 10, 1
01/01/17, 0 , 11, 1
01/01/17, 1 , 12, 1
01/01/17, 2 , 13, 1
01/01/17, 1 , 14, 1
01/01/17, -1, 15, 1
01/01/17, -2, 16, 1
01/01/17, -1, 17, 1
01/01/17, -2, 18, 1
01/01/17, -3, 19, 1
01/01/17, -2, 20, 1
01/01/17, -3, 21, 1
01/01/17, -2, 22, 1
01/01/17, -1, 23, 1
02/01/17, -1, 0 , 2
02/01/17, -1, 1 , 2
02/01/17, -1, 2 , 2
02/01/17, -1, 3 , 2
02/01/17, -1, 4 , 2
02/01/17, -1, 5 , 2
02/01/17, -1, 6 , 2
02/01/17, -1, 7 , 2
02/01/17, -1, 8 , 2
02/01/17, -1, 9 , 2
02/01/17, 0 , 10, 2
02/01/17, 0 , 11, 2
02/01/17, 1 , 12, 2
02/01/17, 1 , 13, 2
02/01/17, 1 , 14, 2
02/01/17, 1 , 15, 2
02/01/17, 1 , 16, 2
02/01/17, 1 , 17, 2
02/01/17, -1, 18, 2
02/01/17, -3, 19, 2
02/01/17, -2, 20, 2
02/01/17, -2, 21, 2
02/01/17, -2, 22, 2
02/01/17, -1, 23, 2')

现在，让我们尝试按照您的指示进行操作，我并不是试图以最佳方式实现这一目标，而是尝试尽可能地坚持您的原始想法，因此，我将使用几个嵌套循环：

# get the different days
days <- levels(df$date)
# create the A matrix, empty
A <- matrix(nrow = length(days), ncol = length(days))
# iterate
for(i in 1:length(days)) {
  for(j in 1:length(days)) {
    # get all the temperatures available for each day
    ci <- df[df$date == days[i],]$temp
    cj <- df[df$date == days[j],]$temp
    # update the A matrix
    A[i, j] <- sum((ci - cj)^2)
  }
}
# finally the last sum
Aj <- unlist(lapply(1:length(days), function(i) sum(A[i, ])))

结果是：

> A
     [,1] [,2]
[1,]    0   97
[2,]   97    0

> Aj
[1] 97 97

这应该可以工作任意天数，并且可以每天进行任意多次温度测量（不一定是24天）。