Apply boolean function to column in data.table in R

Question

I am looking to find the "AND" or "OR" of all the elements by grouping based on column a in a data.table. I haven't been able to find any library that I could use. Any suggestions would be great. Thanks.

set.seed(1)
dt <- data.table(a = sample(seq.int(1,100,1),100,replace =TRUE),b = sample(c(TRUE,FALSE),100,replace = TRUE))
# head(dt)
#       a     b
#  1:  27 FALSE
#  2:  38  TRUE
#  3:  58  TRUE
#  4:  91 FALSE
#  5:  21 FALSE
#  6:  90  TRUE

Answer 1

Perhaps we need

dt[, if(all(b)) .SD , by = a]
dt[, if(any(b)) .SD ,by = a]

If we need to extract the 'a' elements

dt[, if(all(b)) a, by = a]$V1