Description Usage Arguments Details Value Author(s)
read.table
admits that it's not so good at reading large tables with many
columns.
read.table
recommends using scan
, but scan
is tricky unless you know the number of columns.
NCOL is easy & VERY fast to determine on systems with awk
.
This function essentially mashes the results from scan
into a data.frame
On a 15MB file with 16x88742 elements, I got a 19x speed improvement using
this (25.5s) vs read.table
(484.5s).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | read.table.wide(file, header = FALSE, sep = "", quote = if (identical(sep,
"\n")) "" else "\"", dec = ".", row.names, col.names,
as.is = !stringsAsFactors, na.strings = "NA", colClasses = NA,
nrows = -1, skip = 0, check.names = TRUE, fill = !blank.lines.skip,
strip.white = FALSE, blank.lines.skip = TRUE, comment.char = "#",
allowEscapes = FALSE, flush = FALSE,
stringsAsFactors = default.stringsAsFactors(), fileEncoding = "",
encoding = "unknown")
read.delim.wide(file, header = TRUE, sep = "\t", quote = "\"",
dec = ".", fill = TRUE, comment.char = "", ...)
read.csv.wide(file, header = TRUE, sep = ",", quote = "\"", dec = ".",
fill = TRUE, comment.char = "", ...)
|
file |
the name of the file which the data are to be read from.
Each row of the table appears as one line of the file. If it
does not contain an absolute path, the file name is
relative to the current working directory, Alternatively,
|
header |
a logical value indicating whether the file contains the names of the variables as its first line. If missing, the value is determined from the file format: ‘header’ is set to ‘TRUE’ if and only if the first row contains one fewer field than the number of columns. |
sep |
the field separator character. Values on each line of the
file are separated by this character. If ‘sep = “”’ (the
default for |
quote |
the set of quoting characters. To disable quoting altogether,
use ‘quote = “”’. See |
dec |
the character used in the file for decimal points. |
row.names |
a vector of row names. This can be a vector giving the actual row names, or a single number giving the column of the table which contains the row names, or character string giving the name of the table column containing the row names. If there is a header and the first row contains one fewer field than the number of columns, the first column in the input is used for the row names. Otherwise if ‘row.names’ is missing, the rows are numbered. Using ‘row.names = NULL’ forces row numbering. Missing or
‘NULL’ ‘row.names’ generate row names that are considered to
be ‘automatic’ (and not preserved by |
col.names |
a vector of optional names for the variables. The default is to use ‘“V”’ followed by the column number. |
as.is |
the default behavior of Note: to suppress all conversions including those of numeric columns, set ‘colClasses = “character”’. Note that ‘as.is’ is specified per column (not per variable) and so includes the column of row names (if any) and any columns to be skipped. |
na.strings |
a character vector of strings which are to be interpreted as ‘NA’ values. Blank fields are also considered to be missing values in logical, integer, numeric and complex fields. |
colClasses |
character. A vector of classes to be assumed for the columns. Recycled as necessary, or if the character vector is named, unspecified values are taken to be ‘NA’. Possible values are ‘NA’ (the default, when ‘type.convert’ is used), ‘“NULL”’ (when the column is skipped), one of the atomic vector classes (logical, integer, numeric, complex, character, raw), or ‘“factor”’, ‘“Date”’ or ‘“POSIXct”’. Otherwise there needs to be an ‘as’ method (from package ‘methods’) for conversion from ‘“character”’ to the specified formal class. Note that ‘colClasses’ is specified per column (not per variable) and so includes the column of row names (if any). |
nrows |
integer: the maximum number of rows to read in. Negative and other invalid values are ignored. |
skip |
integer: the number of lines of the data file to skip before beginning to read data. |
check.names |
logical. If ‘TRUE’ then the names of the variables in the data frame are checked to ensure that they are syntactically valid variable names. If necessary they are adjusted (by ‘make.names’) so that they are, and also to ensure that there are no duplicates. |
fill |
logical. If ‘TRUE’ then in case the rows have unequal length, blank fields are implicitly added. See ‘Details’. |
strip.white |
logical. Used only when ‘sep’ has been specified, and
allows the stripping of leading and trailing white space from
|
blank.lines.skip |
logical: if ‘TRUE’ blank lines in the input are ignored. |
comment.char |
character: a character vector of length one containing a single character or an empty string. Use ‘“”’ to turn off the interpretation of comments altogether. |
allowEscapes |
logical. Should C-style escapes such as ‘\n’ be
processed or read verbatim (the default)? Note that if not
within quotes these could be interpreted as a delimiter (but
not as a comment character). For more details see |
flush |
logical: if ‘TRUE’, |
stringsAsFactors |
logical: should character vectors be converted to factors? Note that this is overridden by ‘as.is’ and ‘colClasses’, both of which allow finer control. |
fileEncoding |
character string: if non-empty declares the encoding used
on a file (not a connection) so the character data can be
re-encoded. See the ‘Encoding’ section of the help for
|
encoding |
encoding to be assumed for input strings. It is used to mark character strings as known to be in Latin-1 or UTF-8 (see ‘Encoding’): it is not used to re-encode the input, but allows R to handle encoded strings in their native encoding (if one of those two). See ‘Value’. |
... |
Further arguments to be passed to |
Common Error:
The message: ‘Error in FUN(X[[1L]], ...) : the first argument must be of mode character’ means
you should set stringsAsFactors=FALSE
.
A data.frame
containing a representation of the data in the file.
Mark Cowley, 2011-03-29
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