DataTable objects

Description

The DataTable virtual class provides an interface for the storing rectangular data sets, like a basic data.frame object. It extends Sequence.

Accessors

In the following code snippets, 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)).

Subsetting

In the code snippets below, 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.

window(x, start = NA, end = NA, width = NA, frequency = NULL, delta = NULL, ...): Extract the subsequence window from the DataTable object using:

start, end, width

The start, end, or width of the window. Two of the three are required.

frequency, delta

Optional arguments that specify the sampling frequency and increment within the window.

In general, this is more efficient than using "[" operator.

window(x, start = NA, end = NA, width = NA, keepLength = TRUE) <- value: Replace the subsequence window specified on the left (i.e. the subsequence in x specified by start, end and width) by value. value must either be of class class(x), belong to a subclass of class(x), be coercible to class(x), or be NULL. If keepLength is TRUE, the number of rows of value are repeated to create a DataTable with the same number of rows as the width of the subsequence window it is replacing. If keepLength is FALSE, this replacement method can modify the number of rows of x, depending on how the number of rows of the left subsequence window compares to the number of rows of value.

seqselect(x, start=NULL, end=NULL, width=NULL): Similar to window, except that multiple subsequences can be requested. The requested subsequences are concatenated.

seqselect(x, start=NULL, end=NULL, width=NULL) <- value: Similar to window<-, except that multiple consecutive subsequences can be replaced by a value that spans those windows.

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:

subset

logical expression indicating rows to keep, where missing values are taken as FALSE.

select

expression indicating columns to keep.

drop

passed on to [ 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.

Combining

In the code snippets below, 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 ....

Looping

In the code snippets below, x is a DataTable object.

aggregate(x, by, FUN, start = NULL, end = NULL, width = NULL, frequency = NULL, delta = NULL, ..., simplify = TRUE): Generates summaries on the specified windows and returns the result in a convenient form:

by

An object with start, end, and width methods.

FUN

The function, found via match.fun, to be applied to each window of x.

start, end, width

the start, end, or width of the window. If by is missing, then must supply two of the three.

frequency, delta

Optional arguments that specify the sampling frequency and increment within the window.

...

Further arguments for FUN.

simplify

A logical value specifying whether or not the result should be simplified to a vector or matrix if possible.

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.

Coercion

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.

See Also

DataTable-stats for statistical functionality, like fitting regression models, DataFrame-class for an implementation that mimics data.frame, Sequence-class

Examples

  showClass("DataTable")  # shows (some of) the known subclasses