CODEWITHSUNDEEP
rdata.table
Cron Merdek
Cron Merdek

Reputation: 1124

Select rows where all values are TRUE by group, using data.table

I have data with a grouping variable 'group' and a logical variable 'logic'.

library(data.table)
library(dplyr)

dt <- data.table(
    logic = c(TRUE, TRUE, FALSE, TRUE, TRUE, TRUE),
    group = c("A" , "A",  "A"  , "B" , "B" , "B")
)

I would like to filter groups, where all values in the 'logic' column are TRUE.

dplyr works as expected, and keeps only group = B

dt %>% 
  group_by(group) %>% 
  filter(all(logic))
# Source: local data table [3 x 2]
# Groups: group

#   logic group
# 1  TRUE     B
# 2  TRUE     B
# 3  TRUE     B

However, my attempts with data.table have failed, either bringing all table or nothing.

dt[all(logic), group, by = group]
# Empty data.table (0 rows) of 2 cols: group,group

dt[all(.SD$logic), group,by = group]
#    group group
# 1:     A     A
# 2:     B     B

Upvotes: 13

Views: 4315

Answers (2)

talat
talat

Reputation: 70296

You could use [ as in 

dt[, .SD[all(logic)], by = group]
#   group logic
#1:     B  TRUE
#2:     B  TRUE
#3:     B  TRUE

Upvotes: 17

akrun
akrun

Reputation: 887501

We need to use if

dt[, if(all(logic)) .SD, by = group]
#    group logic
#1:     B  TRUE
#2:     B  TRUE
#3:     B  TRUE

Upvotes: 8

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