使用 difftime 遍历行

Question

我在timefact

下有一栏时间

> head(foo)
  cnrd_marsh            timefact timefact_hour
1         БЧ 2016-04-07 14:34:00            14
2         БЧ 2016-04-07 14:15:00            14
3         БЧ 2016-04-07 14:10:00            14
4         БЧ 2016-04-07 13:58:00            13
5         БЧ 2016-04-07 13:57:00            13
6         БЧ 2016-04-07 13:39:00            13

我的 objective 是创建第四列，其中包含整数值，表示给定行与其上一行之间的分钟数差异 (difftime)。此外，我需要排除 timefact_hour 与上面的行不同的所有情况换句话说，我只需要找到共享相同 hour.

的行的差异

我能够编写以下代码，它的工作原理是它从一行到下一行取不同，但它不会将 posix 次转换为字符，也不会跳过实例hour 不同。

output1 <- data.frame("timefact" = character(), diff_time = numeric(0)) 

for (i in 2:nrow(foo)){

  diff_time <- difftime(foo[i, "timefact"], foo[i-1, "timefact"], tz = "EST", units = "mins")
  new_row <- c(foo[i, "timefact"], diff_time)
  output1[nrow(output1) + 1,] = new_row

}

> head(output1)
  timefact diff_time
1     <NA>       -19
2     <NA>        -5
3     <NA>       -12
4     <NA>        -1
5     <NA>       -18
6     <NA>       -31

示例数据如下：

> dput(foo)
structure(list(cnrd_marsh = structure(c(91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 
91L, 91L, 91L, 91L), .Label = c("", "1", "10", "11", "11К", 
"12", "13", "14", "15", "16", "17", "18", "19", "1К", "2", "20", 
"21", "22", "23", "24", "26", "27", "28", "29", "3", "30", "31", 
"32", "33", "33К", "34", "34К", "35", "36", "37", "38", "39", 
"4", "40", "41", "42", "43", "43К", "44", "45", "47", "48", 
"49", "50", "51", "52", "53", "54", "55", "56", "57", "58", "59", 
"6", "60", "61", "62", "63", "63К", "64", "65", "66", "67", 
"7", "70", "70К", "71", "72", "73", "74", "76", "77", "78", 
"79", "8", "80", "81", "82", "83", "84", "85", "86", "88", "9", 
"БК", "БЧ"), class = "factor"), timefact = structure(c(1460057640, 
1460056500, 1460056200, 1460055480, 1460055420, 1460054340, 1460052480, 
1460052360, 1460051340, 1460051040, 1460050440, 1460050380, 1460049360, 
1460048160, 1460048040, 1460046960, 1460046720, 1460046300, 1460045340, 
1460045160, 1460043540, 1460042880, 1460042520, 1460041920, 1460041140, 
1460040120, 1460039760, 1460038860, 1460038620, 1460038080, 1460038020, 
1460037240, 1460036280, 1460035800, 1460034960, 1460034780, 1460034120, 
1460034060, 1460033340, 1460032500, 1460032140, 1460031300, 1460031000, 
1460030340, 1460030340, 1460029800, 1460029200, 1460028300, 1460025720, 
1460090700, 1460088660, 1460088600, 1460087760, 1460087580, 1460086980, 
1460086980, 1460086320, 1460085300, 1460085180, 1460084340, 1460084160, 
1460083620, 1460083620, 1460082780, 1460081820, 1460081760, 1460080740, 
1460080500, 1460080200, 1460079360, 1460079180, 1460077260, 1460076840, 
1460076600, 1460076360, 1460075820, 1460074740, 1460070660, 1460070480, 
1460069100, 1460068800, 1460068140, 1460068140, 1460067060, 1460063880, 
1460063460, 1460062380, 1460062080, 1460061360, 1460061300, 1460059920, 
1460057880, 1460057640, 1460060760, 1460060580, 1460059080, 1460058780, 
1460058240, 1460058180, 1460057220), class = c("POSIXct", "POSIXt"
), tzone = "EST"), timefact_hour = c(14L, 14L, 14L, 13L, 13L, 
13L, 13L, 13L, 12L, 12L, 12L, 12L, 12L, 11L, 11L, 11L, 11L, 11L, 
11L, 11L, 10L, 10L, 10L, 10L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 8L, 
8L, 8L, 8L, 8L, 8L, 8L, 7L, 7L, 7L, 7L, 7L, 6L, 6L, 6L, 6L, 6L, 
5L, 23L, 23L, 23L, 22L, 22L, 22L, 22L, 22L, 22L, 22L, 21L, 21L, 
21L, 21L, 21L, 21L, 21L, 20L, 20L, 20L, 20L, 20L, 20L, 19L, 19L, 
19L, 19L, 19L, 18L, 18L, 17L, 17L, 17L, 17L, 17L, 16L, 16L, 15L, 
15L, 15L, 15L, 15L, 14L, 14L, 15L, 15L, 14L, 14L, 14L, 14L, 14L
)), .Names = c("cnrd_marsh", "timefact", "timefact_hour"), row.names = c(NA, 
-100L), class = "data.frame")

请问如何修改代码才能得到正确的输出。这是输出应该是什么样子的示例

   > head(output)
  cnrd_marsh            timefact timefact_hour timefact_diff
1         БЧ 2016-04-07 14:34:00            14            NA
2         БЧ 2016-04-07 14:15:00            14            19
3         БЧ 2016-04-07 14:10:00            14             5
4         БЧ 2016-04-07 13:58:00            13            NA
5         БЧ 2016-04-07 13:57:00            13             1
6         БЧ 2016-04-07 13:39:00            13            18

Answer 1

最简单的方法可能是像这样使用 data.table。

编辑：由于 timefact_hour 的混淆，通常的分组会产生意想不到的结果。因此，我们可以预先添加 i 过滤器以检查 timefact_hour 是否发生变化。第一个 [ 是为 timefact 创建滞后变量以辅助 diff_time 计算。如果需要，可以在之后将其删除。

require(data.table)
setDT(foo)
foo[, lag.timefact := shift(timefact)][which(timefact_hour-lag(timefact_hour)== 0), diff_time := difftime(lag.timefact, timefact, tz = "EST", units = "mins")]

Answer 2

这是一个可能的解决方案

library(dplyr)

#a is your data.frame

#Create leads of your timefact  & timefact_hour column
# Use ifelse to assign a value to difftime depending on if leading timefact and current timefact is equal or not

b= lead(a$timefact)

a$DiffTimes = c(NA, ifelse(a$timefact_hour[-nrow(a)] == lead(a$timefact_hour)[-nrow(a)], difftime(a$timefact[-nrow(a)], b[-nrow(a)], units = "mins",tz="EST"),NA))

> head(a)
     cnrd_marsh       timefact              timefact_hour DiffTimes
 1 <U+0411><U+0427> 2016-04-07 14:34:00            14        NA
 2 <U+0411><U+0427> 2016-04-07 14:15:00            14        19
 3 <U+0411><U+0427> 2016-04-07 14:10:00            14         5
 4 <U+0411><U+0427> 2016-04-07 13:58:00            13        NA
 5 <U+0411><U+0427> 2016-04-07 13:57:00            13         1
 6 <U+0411><U+0427> 2016-04-07 13:39:00            13        18

使用 difftime 遍历行

looping over rows with difftime

r

loops

row

difftime