Read in a table and show first X rows and columns

The purpose of this function is combine the functionality of read.table and print, which are often used together.

The purpose of this function is to read table from a file into a variable and simultaneously display a preview of the data, showing either the first few rows or columns based on the user's specification. It is important to emphasize that the function expects the user to assign the result of the read operation to a variable in order to achieve its intended purpose. eg. Use var1 = read.table.print(file1) instead of read.table.print(file1)

Usage

read.table.print(
  file,
  header = FALSE,
  sep = "",
  quote = "\"'",
  dec = ".",
  numerals = c("allow.loss", "warn.loss", "no.loss"),
  row.names,
  col.names,
  as.is = TRUE,
  na.strings = "NA",
  colClasses = NA,
  nrows = -1,
  skip = 0,
  check.names = TRUE,
  fill = NULL,
  strip.white = FALSE,
  blank.lines.skip = TRUE,
  comment.char = "#",
  allowEscapes = FALSE,
  flush = FALSE,
  stringsAsFactors = FALSE,
  fileEncoding = "",
  encoding = "unknown",
  skipNul = FALSE,
  dim = c(10L, 5L),
  ...
)

Arguments

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, getwd(). Tilde-expansion is performed where supported. This can be a compressed file (see file).

Alternatively, file can be a readable text-mode connection (which will be opened for reading if necessary, and if so closed (and hence destroyed) at the end of the function call). (If stdin() is used, the prompts for lines may be somewhat confusing. Terminate input with a blank line or an EOF signal, Ctrl-D on Unix and Ctrl-Z on Windows. Any pushback on stdin() will be cleared before return.)

file can also be a complete URL. (For the supported URL schemes, see the ‘URLs’ section of the help for url.)

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 read.table) the separator is ‘white space’, that is one or more spaces, tabs, newlines or carriage returns.

quote

the set of quoting characters. To disable quoting altogether, use quote = "". See scan for the behaviour on quotes embedded in quotes. Quoting is only considered for columns read as character, which is all of them unless colClasses is specified.

dec

the character used in the file for decimal points.

numerals

string indicating how to convert numbers whose conversion to double precision would lose accuracy, see type.convert. Can be abbreviated. (Applies also to complex-number inputs.)

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 as.matrix).

col.names

a vector of optional names for the variables. The default is to use "V" followed by the column number.

as.is

controls conversion of character variables (insofar as they are not converted to logical, numeric or complex) to factors, if not otherwise specified by colClasses. Its value is either a vector of logicals (values are recycled if necessary), or a vector of numeric or character indices which specify which columns should not be converted to factors.

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. Note that the test happens after white space is stripped from the input, so na.strings values may need their own white space stripped in advance.

colClasses

character. A vector of classes to be assumed for the columns. If unnamed, recycled as necessary. If named, names are matched with unspecified values being 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 unquoted character fields (numeric fields are always stripped). See scan for further details (including the exact meaning of ‘white space’), remembering that the columns may include the row names.

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 scan.

flush

logical: if TRUE, scan will flush to the end of the line after reading the last of the fields requested. This allows putting comments after the last field.

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 file, the ‘R Data Import/Export Manual’ and ‘Note’.

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’ and ‘Note’.

skipNul

logical: should nuls be skipped?

dim

dimension of table content to show

...

Further arguments to be passed to read.table.

Value

read table content and a print out of the data head

Details

Read a dataset of type table and show x rows and y columns

Examples

if (FALSE) {
# Example: read a table file and print the first 10 lines
# declare file
new.file <- "test.csv"

# read file and preview default
dth3 <- read.table.print(file = new.file, sep=",",quote = "\"",dec = ".",
fill = TRUE, comment.char = "", header = TRUE)

# read file and preview 10 rows and all columns
dth1 <- read.table.print(file = new.file, sep=",",quote = "\"",dec = ".",
fill = TRUE, comment.char = "", header = TRUE, dim = 10)

# read file and preview 10 rows and 5 columns
dth2 <- read.table.print(file = new.file, sep=",",quote = "\"",dec = ".",
fill = TRUE, comment.char = "", header = TRUE, dim = c(10,5))
}