Transformations of Response or Input Variables
1 2 3 4 
data 
an object of class 
numeric_trafo 
a function to by applied to 
ordered_trafo 
a function to by applied to 
factor_trafo 
a function to by applied to 
surv_trafo 
a function to by applied to
elements of class 
var_trafo 
an optional named list of functions to be applied to the
corresponding variables in 
x 
a factor 
trafo
applies its arguments to the elements of data
according to the classes of the elements. See Transformations
for more documentation and examples.
In the presence of missing values, one needs to make sure that all usersupplied functions deal with that.
A named matrix with nrow(data)
rows and
arbitrary number of columns.
1 2 3 4 5 6  ### rank a variable
ptrafo(data.frame(y = 1:20),
numeric_trafo = function(x) rank(x, na.last = "keep"))
### dummy coding of a factor
ptrafo(data.frame(y = gl(3, 9)))

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