further data.frame-like consistency in j: logical vector

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
42/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
r
Domain
data

Research direction

Start by reading the comparison with data.frame and the related issue #1188, then locate the data.table subsetting implementation and its tests for logical column vectors. Reproduce the sapply(DF, is.numeric) examples before changing anything. Done means the data.table result is consistent with the data.frame result, with regression coverage for this case.

Written by the indexing model from the issue text.

Description

programming

This is simply an extension of #1188 asking for data.frame-like consistency with respect to another common subsetting operation:

set.seed(2030)
DF = data.frame(a = LETTERS, b = letters, c = rnorm(26), d = rnorm(26), e = as.factor(1:26))
DF[ , sapply(DF, is.numeric)]
#              c            d
# 1   1.22587150  0.654058019
# 2  -1.02641266  1.442031659
# 3  -1.33873014 -0.442854108
# --TRUNCATED --
# 24  0.73060958  0.513225722
# 25  0.33502260  0.543853894
# 26  0.53034743 -1.786070335

setDT(DF)
DF[ , sapply(DF, is.numeric)]
#     a     b     c     d     e 
# FALSE FALSE  TRUE  TRUE FALSE 

For now, the workaround is to wrap sapply in which. But here is another case where the data.frame code is more readable and I think unambiguous.

Dominant language
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