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CJ(letters, letters) fails (duplicate column name) #7873

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CJ(letters, letters) fails (duplicate column name)#7873

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@MichaelChirico
MichaelChirico
opened on Jul 31, 2026

I don't recall this being an issue previously so I bet this is a regression:

CJ(letters, letters)
# Error in CJ(letters, letters) : 
#   CJ() cannot create a keyed data.table with duplicated column names: [letters]

While I think it's intentional to prevent creating tables with duplicate names, I think it'd be friendlier to give unique names by default rather than error.

Note that sorted=FALSE fixes this:

CJ(letters, letters, sorted=FALSE)

Activity

  1. rikivillalba commented on Aug 12, 2026

    @rikivillalba
    rikivillalba
    on Aug 12, 2026
    Contributor

    Since CJ is somethin akin to data.table() one might add check.names= with FALSE by default (to preserve current behaviour) or with TRUE by default (to be friendlier) ...

  2. ben-schwen commented on Aug 19, 2026

    @ben-schwen
    ben-schwen
    on Aug 19, 2026
    Member

    This is due to #7760

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