subset.data.table | R Documentation |
Returns subsets of a data.table
.
## S3 method for class 'data.table'
subset(x, subset, select, ...)
x |
|
subset |
logical expression indicating elements or rows to keep |
select |
expression indicating columns to select from |
... |
further arguments to be passed to or from other methods |
The subset
argument works on the rows and will be evaluated
in the data.table
so columns can be referred to (by name) as variables
in the expression.
The data.table
that is returned will maintain the original keys
as long as they are not select
-ed out.
A data.table
containing the subset of rows and columns that are
selected.
subset
DT <- data.table(a=sample(c('a', 'b', 'c'), 20, replace=TRUE),
b=sample(c('a', 'b', 'c'), 20, replace=TRUE),
c=sample(20), key=c('a', 'b'))
sub <- subset(DT, a == 'a')
all.equal(key(sub), key(DT))
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