reorder.factor {gdata} | R Documentation |
Reorder the levels of a factor
## S3 method for class 'factor': reorder(x, order, X, FUN, sort=mixedsort, make.ordered = is.ordered(x), ... )
x |
factor. |
order |
A vector of indexes or a vector of label names giving the order of the new factor levels. |
X |
auxillary data vector |
FUN |
function to be applied to subsets of X determined by
x , to determine factor order. |
sort |
function to use to sort the factor level names |
make.ordered |
logical value indicating whether the returned
object should be an 'ordered' factor. |
... |
Optional parameters to FUN. |
This function changes the order of the levels of a factor. It can do
so via three different mechanisms, depending on whether order
,
X
and FUN
, or sort
are provided.
If order
is provided: For a numeric vector, the new factor level names
are constructed by reordering the factor levels according to the
numeric values. For vectors, order
gives the list of new factor
level names. In either case levels omitted from order
will
become missing values.
If X
and Fun
are provided: The data in X
is grouped by the levels of data
and FUN
is applied.
The groups are then sorted by this value, and the resulting order is
used for the new factor level names.
If sort
is provided (as it is by default): The new
factor level names are generated by applying the supplied function
to the existing factor level names. With order="mixedsort"
the
factor levels are sorted so that combined numeric and character
strings are sorted in according to character rules on the character
sections (including ignoring case), and be numeric rules for the
numeric sections. See mixedsort
for details.
A new factor with the levels ordered as specified.
Gregory R. Warnes Gregory_R_Warnes@groton.pfizer.com
# Create a 4 level example factor trt <- factor( sample( c("PLACEBO","300 MG", "600 MG", "1200 MG"), 100, replace=TRUE ) ) summary(trt) # Note that the levels are not in a meaningful order. # Change the order to something useful # default "mixedsort" ordering trt2 <- reorder(trt) summary(trt2) # using indexes: trt3 <- reorder(trt, c(4,2,3,1)) summary(trt3) # using label names: trt4 <- reorder(trt, c("PLACEBO","300 MG", "600 MG", "1200 MG") ) summary(trt4) # using frequency trt5 <- reorder(trt, X=as.numeric(trt), FUN=length) summary(trt5) # drop out the '300 MG' level trt6 <- reorder(trt, c("PLACEBO", "600 MG", "1200 MG") ) summary(trt6)