x is a DataTable.
nrow(x), ncol(x):
Get the number of rows and columns, respectively.
NROW(x), NCOL(x):
Same as nrow(x) and ncol(x), respectively.
dim(x):
Length two integer vector defined as c(nrow(x), ncol(x)).
rownames(x), colnames(x):
Get the names of the rows and columns, respectively.
dimnames(x):
Length two list of character vectors defined as
list(rownames(x), colnames(x)).
x is a DataTable object. x[i, j, drop=TRUE]:
Return a new DataTable object made of the selected rows and columns. For
single column selection, the drop argument specifies whether or not
to coerce the returned sequence to a standard vector.
head(x, n=6L):
If n is non-negative, returns the first n rows of the DataTable
object.
If n is negative, returns all but the last abs(n) rows of
the DataTable object.
tail(x, n=6L):
If n is non-negative, returns the last n rows of the DataTable
object.
If n is negative, returns all but the first abs(n) rows of
the DataTable object.
subset(x, subset, select, drop=FALSE):
Return a new DataTable object using:
[ indexing operator.na.omit(object):
Returns a subset with incomplete cases removed.
na.exclude(object):
Returns a subset with incomplete cases removed (but to be
included with NAs in statistical results).
is.na(x):
Returns a logical matrix indicating which cells are missing.
complete.cases(x):
Returns a logical vector identifying which cases have no missing values.
x is a DataTable object. cbind(...): Creates a new DataTable by combining the columns
of the DataTable objects in ....
rbind(...): Creates a new DataTable by combining the rows of
the DataTable objects in ....
merge(x, y, ...): Merges two DataTable
objects x and y, with arguments in ... being
the same as those allowed by the base merge. It is
allowed for either x or y to be a data.frame.
x is a DataTable object. by(data, INDICES, FUN, ..., simplify = TRUE):
Apply FUN to each group of data, a DataTable,
formed by the factor (or list of factors) INDICES. Exactly
the same contract as as.data.frame.
duplicated(x): Returns a logical vector indicating the rows
that are identical to a previous row.
unique(x): Returns a new DataTable after
removing the duplicated rows from x.
show(x):
By default the show method displays 5 head and 5 tail
lines. The number of lines can be altered by setting the global
options showHeadLines and showTailLines. If the
object length is less than the sum of the options, the full object
is displayed. These options affect GRanges, GAlignments,
Ranges, DataTable and XString objects.
as.env(x, enclos = parent.frame()):
Creates an environment from x with a symbol for each
colnames(x). The values are not actually copied into the
environment. Rather, they are dynamically bound using
makeActiveBinding. This prevents unnecessary copying
of the data from the external vectors into R vectors. The values
are cached, so that the data is not copied every time the symbol
is accessed.
xtabs(formula = ~., data, subset, na.action,
exclude = c(NA, NaN), drop.unused.levels = FALSE):
Like the original xtabs, except data is a
DataTable.
data.frame.
showClass("DataTable") # shows (some of) the known subclasses
library(IRanges)
df <- DataFrame(as.data.frame(UCBAdmissions))
xtabs(Freq ~ Gender + Admit, df)
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