It looks like custom attributes are lost by a DF to DT creation, and when the key info for a DT is invalidated, altered, etc... I ran into this when trying to attach some attribute info to a table that identifies column groups so that a new global variable or passing another param to functions wouldn't be needed. This worked nicely, until I had need to either modify some data in the table, which invalidates the key...
Was this a design decision? If so, why? Example:: > df <- data.frame( id=c(1:5), name= letters[1:5] ) > attr(df, 'testing') <- 'keep me' > attr(df, 'testing') [1] "keep me" > dt <- data.table( df ) > attr(dt, 'testing') NULL > attr(dt, 'testing') <- 'keep me' > attr(dt, 'testing') [1] "keep me" > df[ 5 , 'id' ] <- 53 > dt[ 5 , 'id' ] <- 53 > attr(df, 'testing') [1] "keep me" > attr(dt, 'testing') [1] "keep me" > setkey(dt) > attr(dt, 'testing') NULL > attr(dt, 'testing') <- 'keep me' > attr(dt, 'testing') [1] "keep me" > dt[ 5 , 'id' ] <- 3 > attr(dt, 'testing') [1] "keep me" > key(dt) NULL > -- Sincerely, Thell
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