| data.frame {base} | R Documentation |
The function data.frame() creates data frames, tightly coupled
collections of variables which share many of the properties of
matrices and of lists, used as the fundamental data structure by most
of R's modeling software.
data.frame(..., row.names = NULL, check.rows = FALSE,
check.names = TRUE, fix.empty.names = TRUE,
stringsAsFactors = default.stringsAsFactors())
default.stringsAsFactors()
... |
these arguments are of either the form |
row.names |
|
check.rows |
if |
check.names |
logical. If |
fix.empty.names |
logical indicating if arguments which are
“unnamed” (in the sense of not being formally called as
|
stringsAsFactors |
logical: should character vectors be converted
to factors? The ‘factory-fresh’ default is |
A data frame is a list of variables of the same number of rows with
unique row names, given class "data.frame". If no variables
are included, the row names determine the number of rows.
The column names should be non-empty, and attempts to use empty names
will have unsupported results. Duplicate column names are allowed,
but you need to use check.names = FALSE for data.frame
to generate such a data frame. However, not all operations on data
frames will preserve duplicated column names: for example matrix-like
subsetting will force column names in the result to be unique.
data.frame converts each of its arguments to a data frame by
calling as.data.frame(optional = TRUE). As that is a
generic function, methods can be written to change the behaviour of
arguments according to their classes: R comes with many such methods.
Character variables passed to data.frame are converted to
factor columns unless protected by I or argument
stringsAsFactors is false. If a list or data
frame or matrix is passed to data.frame it is as if each
component or column had been passed as a separate argument (except for
matrices protected by I).
Objects passed to data.frame should have the same number of
rows, but atomic vectors (see is.vector), factors and
character vectors protected by I will be recycled a
whole number of times if necessary (including as elements of list
arguments).
If row names are not supplied in the call to data.frame, the
row names are taken from the first component that has suitable names,
for example a named vector or a matrix with rownames or a data frame.
(If that component is subsequently recycled, the names are discarded
with a warning.) If row.names was supplied as NULL or no
suitable component was found the row names are the integer sequence
starting at one (and such row names are considered to be
‘automatic’, and not preserved by as.matrix).
If row names are supplied of length one and the data frame has a
single row, the row.names is taken to specify the row names and
not a column (by name or number).
Names are removed from vector inputs not protected by I.
default.stringsAsFactors is a utility that takes
getOption("stringsAsFactors") and ensures the result is
TRUE or FALSE (or throws an error if the value is not
NULL).
A data frame, a matrix-like structure whose columns may be of differing types (numeric, logical, factor and character and so on).
How the names of the data frame are created is complex, and the rest
of this paragraph is only the basic story. If the arguments are all
named and simple objects (not lists, matrices of data frames) then the
argument names give the column names. For an unnamed simple argument,
a deparsed version of the argument is used as the name (with an
enclosing I(...) removed). For a named matrix/list/data frame
argument with more than one named column, the names of the columns are
the name of the argument followed by a dot and the column name inside
the argument: if the argument is unnamed, the argument's column names
are used. For a named or unnamed matrix/list/data frame argument that
contains a single column, the column name in the result is the column
name in the argument. Finally, the names are adjusted to be unique
and syntactically valid unless check.names = FALSE.
In versions of R prior to 2.4.0 row.names had to be
character: to ensure compatibility with such versions of R, supply
a character vector as the row.names argument.
Chambers, J. M. (1992) Data for models. Chapter 3 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.
I,
plot.data.frame,
print.data.frame,
row.names, names (for the column names),
[.data.frame for subsetting methods
and I(matrix(..)) examples;
Math.data.frame etc, about
Group methods for data.frames;
read.table,
make.names.
L3 <- LETTERS[1:3]
fac <- sample(L3, 10, replace = TRUE)
(d <- data.frame(x = 1, y = 1:10, fac = fac))
## The "same" with automatic column names:
data.frame(1, 1:10, sample(L3, 10, replace = TRUE))
is.data.frame(d)
## do not convert to factor, using I() :
(dd <- cbind(d, char = I(letters[1:10])))
rbind(class = sapply(dd, class), mode = sapply(dd, mode))
stopifnot(1:10 == row.names(d)) # {coercion}
(d0 <- d[, FALSE]) # data frame with 0 columns and 10 rows
(d.0 <- d[FALSE, ]) # <0 rows> data frame (3 named cols)
(d00 <- d0[FALSE, ]) # data frame with 0 columns and 0 rows