为每个ID创建指定数量的观察值

Question

我有一个数据集，具有每人指定数量的记录：

set.seed(99)
# Create values from a Poisson distribution
freqs <- rpois(100, 3) 
# Add an ID to each row
freqs <- as.data.frame(freqs)
freqs$id <- seq_len(nrow(freqs))

我现在希望freqs$freqs中的值是每个ID的观察次数。转换如下所示：

ID    freqs
1      3
2      1
...    ...
3      2

最后是：

ID    freqs
1      3
1      3
1      3
2      1
...    ....
3      2
3      2

Answer 1

一个选项是uncount中的tidyr

library(tidyr)
library(dplyr)
uncount(freqs, freqs, .remove = FALSE)  %>% 
        as_tibble %>% 
        select(id, freqs)

Answer 2

获取ID的另一个tidyverse选项：

plyr::ldply(purrr::map2(freqs$id,freqs$freqs,function(x,y) rep(x,y)),
            data.frame) 

Answer 3

as.data.frame(lapply(freqs, rep, freqs$freqs))

#     freqs id
# 1       3  1
# 2       3  1
# 3       3  1
# 4       1  2
# 5       4  3
# 6       4  3
# 7       4  3
# 8       4  3
# 9       8  4
# 10      8  4
# 11      8  4
# 12      8  4
# 13      8  4
# 14      8  4
# 15      8  4
# 16      8  4  
# ...

或

purrr::map_dfr(freqs, rep, freqs$freqs)

# # A tibble: 293 x 2
#    freqs    id
#    <int> <int>
#  1     3     1
#  2     3     1
#  3     3     1
#  4     1     2
#  5     4     3
#  6     4     3
#  7     4     3
#  8     4     3
#  9     8     4
# 10     8     4
# # ... with 283 more rows