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rbindlist use.names=TRUE returns random column order when ncol>255 #3373

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mattdowle opened this issue Feb 8, 2019 · 2 comments · Fixed by #3455
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rbindlist use.names=TRUE returns random column order when ncol>255 #3373

mattdowle opened this issue Feb 8, 2019 · 2 comments · Fixed by #3455
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@mattdowle
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@mattdowle mattdowle commented Feb 8, 2019

Follow up to #3306. The printing issue there is fixed by not using use.names=TRUE in that case. But rbindlist in general still has the issue. Also see: #3352 (comment)

minimal example:

ncol = 30
DT = setDT(replicate(ncol, rnorm(3L), simplify = FALSE))
identical(colnames(rbind(DT[1], DT[3])), colnames(DT))
# [1] TRUE


ncol = 300
DT = setDT(replicate(ncol, rnorm(3L), simplify = FALSE))
identical(colnames(rbind(DT[1], DT[3])), colnames(DT))
# [1] FALSE
@ChristK
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@ChristK ChristK commented Feb 8, 2019

Possibly related...
rbind changes column order when there are duplicate column names

require(data.table) #v1.12.1 built 2019-02-08 09:09:06 UTC;
dt1 <- data.table(a=1, b=2, c=3, b=4)
dt2 <- data.table(a=1, b=2, c=3, b=4)
rbind(dt1, dt2, use.names = TRUE) # use.names = FALSE does not reorder the columns
# a b b c
# 1: 1 2 4 3
# 2: 1 2 4 3

@MichaelChirico
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@MichaelChirico MichaelChirico commented Feb 8, 2019

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3 participants