Transform {memisc} | R Documentation |
Transform is a variant of transform
that preserves
the attributes of the transformed data frame
and allows for some preliminary computations, which can be used in
variable transformations.
## S3 method for class 'data.frame': Transform(.data.,.expr.,...)
.data. |
The object to be transformed |
.expr. |
an expression or closure (a series of expression inside curly braces). |
... |
Further arguments of the form tag=value |
Transform
is a slightly extended version of transform
.
Thus it only does useful things with data frames.
If an expression is given as second argument (.expr.
) then it
is evaluated with .data.
as environment (that is, the
variables inside this data frame can be accessed directly in the
expression). If this expression returns a list with named elements,
these elements can be accessed in subsequent tag-value assignments.
The modified value of .data.
with all the attributes of .data.
(only the names
attribute is updated, of course).
berkeley <- aggregate(wtable(Admit,Freq)~.,data=UCBAdmissions) Transform(berkeley, list(total=sum(Admitted) + sum(Rejected)), Admitted.p = Admitted/total, Rejected.p = Rejected/total) Transform(berkeley, { total <- sum(Admitted) + sum(Rejected) list(total=total) }, Admitted.p = Admitted/total, Rejected.p = Rejected/total)