I started to use the data.table to subset, reshape large data.
But how do I transform a set of columns?
# for a data.frame I would do:
df = data.frame(a = c("a","b","c","d"), b = 1:4,c = 1:4)
df[,2:3] = df[,2:3]^2
# but with data.table this somehow similar code produces an error.
dt = data.table(a = c("a","b","c","d"), b = 1:4,c = 1:4)
dt[, 2:3 , with=FALSE ] = x[,2:3,with=FALSE]^2
By the way.
I need the columns selection 2:3 because column 1 in data.table
contains the keys.
With data.frame, matrix I would store the keys as rownames.
and just write:
df = df^2
(easier to read)
Is there syntactic sugar in data.table to be able to say something like:
transform all nonkey columns, replace all nonkey columns?
best regards
Witold
--
Witold Eryk Wolski
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