Reorder the levels of a factor
auxillary data vector
function to be applied to subsets of
optional parameters to
logical value indicating whether the returned
object should be an
a vector of indexes or a vector of label names giving the order of the new factor levels
function to use to sort the factor level names, used only
This function changes the order of the levels of a factor. It can do
so via three different mechanisms, depending on whether,
sort are provided.
Fun are provided: The data in
is grouped by the levels of
FUN is applied.
The groups are then sorted by this value, and the resulting order is
used for the new factor level names.
new.order is a numeric vector, the new factor level names
are constructed by reordering the factor levels according to the
numeric values. If
new.order is a chraccter vector,
new.order gives the list of new factor level names. In either
case levels omitted from
new.order will become missing
sort is provided (as it is by default): The new factor level
names are generated by calling the function specified by
to the existing factor level names. With
(the default) 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 the numeric
rules for the numeric sections. See
A new factor with reordered levels
Gregory R. Warnes email@example.com
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# 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, new.order=c(4, 2, 3, 1)) summary(trt3) # - using label names: trt4 <- reorder(trt, new.order=c("PLACEBO", "300 MG", "600 MG", "1200 MG")) summary(trt4) # - using frequency trt5 <- reorder(trt, X=rnorm(100), FUN=mean) summary(trt5) # Drop out the '300 MG' level trt6 <- reorder(trt, new.order=c("PLACEBO", "600 MG", "1200 MG")) summary(trt6)
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