R - Number of times an item from one list appears in another list

user_12918834 0
Viewed 31

I have two lists of patient ID's. One is short, the other is very long.

I'd like to know how many times patients from the short list appear in the long list, preferably using dplyr.

library(tidyr)
library(tidyverse)

shortlist<-tribble(
  ~PatientID, 
  #--
  10,
  11,
  12,
  13,
  14,
  15
)

longlist<-tribble(
  ~PatientID,
  #--
  10,
  10,
  11,
  12,
  12,
  12,
  13,
  14,
  15,
  15,
  15,
  16,
  17
)

Desired output would be something like:

10 2

11 1

12 3

13 1

and so on

purrr dplyr r
3 Answers

We filter the 'PatientID' based on the 'shortlist' and get the count

library(dplyr)
longlist %>% 
  filter(PatientID %in% shortlist$PatientID) %>% 
  count(PatientID)

-output

# A tibble: 6 × 2
  PatientID     n
      <dbl> <int>
1        10     2
2        11     1
3        12     3
4        13     1
5        14     1
6        15     3
user_37322710 
shortlist %>% 
  group_by(PatientID) %>% 
  mutate(count = sum(longlist$PatientID == PatientID))

# A tibble: 6 × 2
# Groups:   PatientID [6]
  PatientID count
      <dbl> <int>
1        10     2
2        11     1
3        12     3
4        13     1
5        14     1
6        15     3
user_172133550

Another possible solution:

library(tidyverse)

table(longlist) %>% 
  stack %>% 
  mutate(PatientID = levels(ind) %>% as.numeric, ind = NULL) %>% 
  left_join(shortlist, ., by = "PatientID")

#> # A tibble: 6 × 2
#>   PatientID values
#>       <dbl>  <int>
#> 1        10      2
#> 2        11      1
#> 3        12      3
#> 4        13      1
#> 5        14      1
#> 6        15      3
user_115644870
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