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giac
giac

Reputation: 4309

R dplyr count in a list

I can't figure how to properly count (or table) in a list object.

So my list is named v and it has 3 elements, is it possible to avoid doing the following ? 

library(dplyr) 

v[[1]] %>% count(group, variable, value)
v[[2]] %>% count(group, variable, value)
v[[3]] %>% count(group, variable, value)

My problem using table is that I have to group several variables (here group, variable and value).

Solution with table, which is not great output 

ft = function(x) table(x)
v %>% lapply(ft)

Output wanted 

[[1]] # list 1
 group variable value     n
  1       V1 FALSE     1
  1       V1  TRUE     2
  1       V2 FALSE     2
  1       V2  TRUE     1
  ... 

 [[2]] # list 2 
 group variable value     n
  1       V1 FALSE     1
  1       V1  TRUE     2
  1       V2 FALSE     3
  1       V2  TRUE     3
... 

# and so on #

Generate the data 

library(purrr) 
library(reshape2) 

v = list('vector', 3)

for(i in 1:3){
  dt = replicate(10, rbernoulli(9)) %>% as.data.frame() 
  dt$group = rep(1:3, 3)
  v[[i]] = dt %>% melt(id.vars = 'group')
}

Upvotes: 1

Views: 896

Answers (2)

akrun
akrun

Reputation: 887251

We can use the purrr package

library(dplyr)
library(purrr)
v %>%
   map(~count(., group, variable, value))
#[[1]]
#Source: local data frame [56 x 4]
#Groups: group, variable [?]

#   group variable value     n
#   <int>   <fctr> <lgl> <int>
#1      1       V1 FALSE     1
#2      1       V1  TRUE     2
#3      1       V2 FALSE     2
#4      1       V2  TRUE     1
#5      1       V3 FALSE     3
#6      1       V4 FALSE     1
#7      1       V4  TRUE     2
#8      1       V5  TRUE     3
#9      1       V6 FALSE     2
#10     1       V6  TRUE     1
#..   ...      ...   ...   ...

#[[2]]
#Source: local data frame [49 x 4]
#Groups: group, variable [?]

#   group variable value     n
#   <int>   <fctr> <lgl> <int>
#1      1       V1 FALSE     3
#2      1       V2 FALSE     2
#3      1       V2  TRUE     1
#4      1       V3 FALSE     2
#5      1       V3  TRUE     1
#6      1       V4  TRUE     3
#7      1       V5  TRUE     3
#8      1       V6 FALSE     1
#9      1       V6  TRUE     2
#10     1       V7 FALSE     1
#..   ...      ...   ...   ...

#[[3]]
#Source: local data frame [54 x 4]
#Groups: group, variable [?]

#   group variable value     n
#   <int>   <fctr> <lgl> <int>
#1      1       V1  TRUE     3
#2      1       V2 FALSE     2
#3      1       V2  TRUE     1
#4      1       V3 FALSE     2
#5      1       V3  TRUE     1
#6      1       V4  TRUE     3
#7      1       V5 FALSE     1
#8      1       V5  TRUE     2
#9      1       V6 FALSE     2
#10     1       V6  TRUE     1
#..   ...      ...   ...   ...

NOTE: Works in purrr_0.2.1 and purrr_0.2.2

Upvotes: 1

Daniel
Daniel

Reputation: 7832

Alternative would be lapply:

v %>% lapply(count, group, variable, value)

or even shorter:

lapply(v, count, group, variable, value)

Upvotes: 2

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