为连续值创建组名

Question

看起来很简单，想不出更简单的方法。我在下面有一个 x 向量，需要为连续值创建组名。我的尝试是使用 rle，更好的主意？

# data
x <- c(1,1,1,2,2,2,3,2,2,1,1)

# make groups
rep(paste0("Group_", 1:length(rle(x)$lengths)), rle(x)$lengths)
# [1] "Group_1" "Group_1" "Group_1" "Group_2" "Group_2" "Group_2" "Group_3" "Group_4"
# [9] "Group_4" "Group_5" "Group_5"

Answer 1

使用 data.table、

中的 rleid

library(data.table)

rleid(x, prefix = "Group_")
#[1] "Group_1" "Group_1" "Group_1" "Group_2" "Group_2" "Group_2" "Group_3" "Group_4" "Group_4" "Group_5" "Group_5"

Answer 2

使用 diff 和 cumsum :

paste0("Group_", cumsum(c(1, diff(x) != 0)))
#[1] "Group_1" "Group_1" "Group_1" "Group_2" "Group_2" "Group_2" "Group_3" "Group_4" "Group_4" "Group_5" "Group_5"

（如果您的值是浮点值，您可能必须避免 != 并改用容差。）

Answer 3

使用 cumsum 但不依赖于数字数据：

paste0("Group_", 1 + c(0, cumsum(x[-length(x)] != x[-1])))


[1] "Group_1" "Group_1" "Group_1" "Group_2" "Group_2" "Group_2" "Group_3" "Group_4" "Group_4" "Group_5" "Group_5"

Answer 4

groupdata2 中的

group() 可以使用 l_starts 方法从组起点列表创建组。通过设置n为auto，它会自动找到组开始：

x <- c(1,1,1,2,2,2,3,2,2,1,1)
groupdata2::group(x, n = "auto", method = "l_starts")

## # A tibble: 11 x 2
## # Groups:   .groups [5]
##     data .groups
##    <dbl> <fct>  
##  1     1 1      
##  2     1 1      
##  3     1 1      
##  4     2 2      
##  5     2 2      
##  6     2 2      
##  7     3 3      
##  8     2 4      
##  9     2 4      
## 10     1 5      
## 11     1 5

还有 differs_from_previous() 函数可以查找与先前值相差某个阈值的值或值的索引。

# The values to start groups at
differs_from_previous(x, threshold = 1,
                      direction = "both")
## [1] 2 3 2 1

# The indices to start groups at
differs_from_previous(x, threshold = 1,
                      direction = "both",
                      return_index = TRUE)
## [1] 4 7 8 10

为连续值创建组名

Create group names for consecutive values

r

run-length-encoding