Gets the rank of the elements in each row (column) of a matrix.
rowRanks(x, rows = NULL, cols = NULL, ties.method = c("max", "average",
"first", "last", "random", "max", "min", "dense"), dim. = dim(x), ...,
useNames = TRUE)colRanks(x, rows = NULL, cols = NULL, ties.method = c("max", "average",
"first", "last", "random", "max", "min", "dense"), dim. = dim(x),
preserveShape = FALSE, ..., useNames = TRUE)
A matrix of type integer is
returned, unless ties.method = "average" when it is of type
numeric.
The rowRanks() function always returns an NxK
matrix, where N (K) is the number of rows (columns)
whose ranks are calculated.
The colRanks() function returns an NxK matrix, if
preserveShape = TRUE, otherwise a KxN matrix.
Any names of x are ignored and absent in the
result.
A vector indicating subset of rows to
operate over. If NULL, no subsetting is done.
A vector indicating subset of columns to
operate over. If NULL, no subsetting is done.
A character string specifying how
ties are treated. For details, see below.
An integer vector of
length two specifying the dimension of x, also when not a
matrix. Comment: The reason for this argument
being named with a period at the end is purely technical (we get a run-time
error if we try to name it dim).
Not used.
If TRUE (default), names
attributes of the result are set, otherwise not.
A logical specifying whether the
matrix returned should preserve the input shape of
x, or not.
Missing values are ranked as NA_integer_, as with na.last = "keep"
in the rank() function.
The implementation is optimized for both speed and memory. To avoid
coercing to doubles (and hence memory allocation),
there is a unique implementation for integer matrices.
Furthermore, it is more memory efficient to do
colRanks(x, preserveShape = TRUE) than
t(colRanks(x, preserveShape = FALSE)).
Hector Corrada Bravo and Harris Jaffee. Peter Langfelder for adding
'ties.method' support. Brian Montgomery for adding more 'ties.method's.
Henrik Bengtsson adapted the original native
implementation of rowRanks() from Robert Gentleman's rowQ() in
the Biobase package.
These functions rank values and treats missing values the same way as
rank().
For equal values ("ties"), argument ties.method determines how these
are ranked among each other. More precisely, for the following values of
ties.method, each index set of ties consists of:
"first" - increasing values that are all unique
"last" - decreasing values that are all unique
"min" - identical values equaling the minimum of
their original ranks
"max" - identical values equaling the maximum of
their original ranks
"average" - identical values that equal the sample mean of
their original ranks. Because the average is calculated, the returned
ranks may be non-integer values
"random" - randomly shuffled values of their original ranks.
"dense" - increasing values that are all unique and,
contrary to "first", never contain any gaps
For more information on ties.method = "dense", see frank() of
the data.table package.
For more information on the other alternatives, see rank().
Note that, due to different randomization strategies, the shuffling order
produced by these functions when using ties.method = "random" does
not reproduce that of rank().
WARNING: For backward-compatibility reasons, the default is
ties.method = "max", which differs from rank()
which uses ties.method = "average" by default.
Since we plan to change the default behavior in a future version, we recommend
to explicitly specify the intended value of argument ties.method.
For developers, see also Section Utility functions' in
'Writing R Extensions manual', particularly the
native functions R_qsort_I() and R_qsort_int_I().