在R中創建具有特定長度的序列

我正在嘗試創建一個路徑序列。以下是示例資料集：

df <- structure(list(
  sess_id = c(4, 4, 4, 4, 4, 4, 4, 7, 7, 7, 7, 7), 
  Page = c("A", "B", "C", "D", "A", "C", "B", "B", "C", "D", "A", "D")),
  .Names = c("sess_id", "Page"),
  row.names = c(NA, -12L),
  class = "data.frame")

這是表格：

我想像這樣添加三列：

我正在嘗試在每個會話中創建一個包含五個頁面的路徑序列。并映射該五頁序列的開始和結束。

uj5u.com熱心網友回復：

使用rollapplyrfrom packagezoo創建每組的滾動序列sess_id。那么序列的第一個和最后一個字符分別是Start和End列。

df <- structure(list(
  sess_id = c(4, 4, 4, 4, 4, 4, 4, 7, 7, 7, 7, 7), 
  Page = c("A", "B", "C", "D", "A", "C", "B", "B", "C", "D", "A", "D")),
  .Names = c("sess_id", "Page"),
  row.names = c(NA, -12L),
  class = "data.frame")


fun <- function(x, width) {
  y1 <- zoo::rollapplyr(x, width = seq(width), paste, collapse = "")[1:(width - 1L)]
  y2 <- zoo::rollapplyr(x, width = width, paste, collapse = "")
  c(y1, y2)
}

sp <- split(df$Page, df$sess_id)
l <- 5L

df$Path <- unlist(lapply(sp, fun, width = l))
df$Start <- substr(df$Path, 1, 1)
df$End <- substring(df$Path, nchar(df$Path))
df
#>    sess_id Page  Path Start End
#> 1        4    A     A     A   A
#> 2        4    B    AB     A   B
#> 3        4    C   ABC     A   C
#> 4        4    D  ABCD     A   D
#> 5        4    A ABCDA     A   A
#> 6        4    C BCDAC     B   C
#> 7        4    B CDACB     C   B
#> 8        7    B     B     B   B
#> 9        7    C    BC     B   C
#> 10       7    D   BCD     B   D
#> 11       7    A  BCDA     B   A
#> 12       7    D BCDAD     B   D

^{使用reprex v2.0.2創建于 2022-11-08}

uj5u.com熱心網友回復：

您可以使用accumulate substr如下所示

library(dplyr)
library(purrr)

df %>%
  group_by(sess_id) %>%
  mutate(Path = accumulate(Page, paste0)) %>%
  ungroup() %>%
  mutate(
    Path = substr(Path, nchar(Path) - 4, nchar(Path)),
    Start = substr(Path, 1, 1),
    End = Page
  )

這使

# A tibble: 12 × 5
   sess_id Page  Path  Start End  
     <dbl> <chr> <chr> <chr> <chr>
 1       4 A     A     A     A
 2       4 B     AB    A     B
 3       4 C     ABC   A     C
 4       4 D     ABCD  A     D
 5       4 A     ABCDA A     A
 6       4 C     BCDAC B     C
 7       4 B     CDACB C     B
 8       7 B     B     B     B
 9       7 C     BC    B     C
10       7 D     BCD   B     D
11       7 A     BCDA  B     A
12       7 D     BCDAD B     D

uj5u.com熱心網友回復：

以下作業并使用 tidyverse。Path最初是在每個字母中的所有字母sess_id粘在一起時創建的。然后取第一個到第 n 個字母，其中 n 是行號。然后從字串末尾取 0 到 5 個字符。

Start和End只是 的第一個和最后一個字母Path。

最后我們設定Path,當Start的長度End為1 時。""Path

df <- df %>% 
  group_by(sess_id) %>% 
  mutate(Path = paste0(Page , collapse = "") %>% 
           str_sub( 1 , row_number()) %>% 
           str_extract( "\\w{0,5}$"),
         
         Start = str_extract(Path , "^\\w"), 
         End = str_extract(Path , "\\w$")) %>% 
  mutate(across(c(Path, Start, End), ~if_else(str_length(Path)==1 , "" , .)))

> df
# A tibble: 12 x 5
# Groups:   sess_id [2]
   sess_id Page  Path    Start End  
     <dbl> <chr> <chr>   <chr> <chr>
 1       4 A     ""      ""    ""   
 2       4 B     "AB"    "A"   "B"  
 3       4 C     "ABC"   "A"   "C"  
 4       4 D     "ABCD"  "A"   "D"  
 5       4 A     "ABCDA" "A"   "A"  
 6       4 C     "BCDAC" "B"   "C"  
 7       4 B     "CDACB" "C"   "B"  
 8       7 B     ""      ""    ""   
 9       7 C     "BC"    "B"   "C"  
10       7 D     "BCD"   "B"   "D"  
11       7 A     "BCDA"  "B"   "A"  
12       7 D     "BCDAD" "B"   "D" 

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