Read: Read Contents of a Data File with Optional Variable Labels...

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Read Contents of a Data File with Optional Variable Labels and Feedback

Description

Abbreviation: rd, rd_lbl, Read2

Reads the contents of the specified data file into an R data table, what R calls a data frame. By default the format of the file is detected from its filetype: comma or tab separated value text file from .csv, SPSS data file from .sav, SAS data from from .sas7bdat, or R data file from .rda, and Excel file from .xls, .xlsx using Alexander Walker's openxlsx package, or .ods using Gerrit-Jan Schutten and Chung-hong Chan plus other contributor's readODS package. Specify a fixed width formatted text data file to be read with the required R widths option. Identify the data file by either browsing for the file on the local computer system with Read(), or identify the file with the first argument a character string in the form of a path name or a web URL (except for .Rda files which must be on the local computer system).

Any variable labels in a native SPSS are automatically included in the data file. See the details section below for more information. Variable labels can also be added and modified individually with the lessR function label, and more comprehensively with the VariableLabels function.

The function provides feedback regarding the data that is read by invoking the lessR function details. The default brief form of this function invoked by default only lists the input files, the variable name table, and any variable labels.

The lessR function corRead reads a correlation matrix.

Usage

Read(from=NULL, format=NULL, var_labels=FALSE, widths=NULL,

         missing="", n_mcut=1,
         miss_show=30, miss_zero=FALSE, miss_matrix=FALSE, 
      
         max_lines=30, sheet=1, row_names=NULL,

         brief=TRUE, quiet=getOption("quiet"),

         fun_call=NULL, ...)

rd(...) 
rd_lbl(..., var_labels=TRUE)
Read2(..., sep=";", dec=",")

Arguments

from	File reference included in quotes, either empty to browse for the data file, a full path name or web URL, or the name of a data file included with lessR, such as "Employee". A URL begins with http://.
format	Format of the data in the file, not usually specified because set by default according to the file type of the file to read: .csv, .tsv or .txt read as a text file, .xls, .xlsx read as an Excel file, or .ods as an OpenDocument Spreadsheet file. .feather and .parquet for the arrow formats for feather and parquet dat files. .sav reads as an SPSS file, which also reads the variable labels if present, .sas7bdat reads as a SAS file, and .rda reads as a native R data file. If the data file is not identified by one of these file types, then explicitly set by setting to one of the following values: "csv", "tsv", "Excel", "feather", "parquet", "R", "SPSS", or "SAS".
var_labels	Set TRUE if reading a csv or Excel file of variable labels into the data frame l in which each row consists of a variable name in the first column and the corresponding variable label in the second column, and perhaps units in the third row if using Regression function to generate automatic markdown files of discursive text.
widths	Specifies the width of the successive columns for fixed width formatted data.

missing	Missing value code, which by default is literally a missing data value in the data table.
n_mcut	For the missing value analysis, list the row name and number of missing values if the number of missing exceeds or equals this cutoff. Requires brief=FALSE.
miss_show	For the missing value analysis, the number of rows, one row per observation, that has as many or missing values as n_mcut. Requires brief=FALSE.
miss_zero	For the missing value analysis, list the variable name or the row name even for values of 0, that is rows with no missing data. By default only variables and rows with missing data are listed. Requires brief=FALSE.
miss_matrix	For the missing value analysis, if there is any missing data, list a version of the complete data table with a 0 for a non-missing value and a 1 for a missing value.

sep	Character that separates adjacent values in a text file of data.
dec	Character that serves as the decimal separator in a number.
max_lines	Maximum number of lines to list of the data and labels.
sheet	For Excel files, specifies the work sheet to read. Provide either the worksheet number according to its position, or its name enclosed in quotes. The default is the first work sheet.
row_names	FALSE by default so no row names from the input data. Set to TRUE to convert the first column of input data to row names. For reading .csv files, can also set to the integer number of the column to convert to row names. For Excel and ODS files, only acceptable value is 1 for the first column.
brief	If TRUE, display only variable names table plus any variable labels.
quiet	If set to TRUE, no text output. Can change the corresponding system default with style function.
fun_call	Function call. Used with Rmd to pass the function call when obtained from the abbreviated function call rd.
...	Other parameter values define with the R read functions, such as the read.table function for text files, with row.names and header.

Details

By default Read reads text data files which are either comma delimited, csv, or tab-delimited data files, native Excel files of type .xls or .xlsx, native ODS files of type .ods, native R files with file type of .rda, native SAS files with file type .sas7bdat, and native SPSS files with file type .sav. Invoke the widths option to allow for the reading of fixed width formatted data. Calls the lessR function details to provide feedback regarding details of the data frame that was read. By default, variables defined by non-numeric variables are read as character strings. To read as factors specify stringsAsFactors as FALSE, unless all the values of a variable a non-numeric and unique, in which case the variable is classified as a character string.

CREATE csv FILE
One way to create a csv data file is to enter the data into a text editor. A more structured method is to use a worksheet application such as MS Excel, LibreOffice Calc, or Apple Numbers. Place the variable names in the first row of the worksheet. Each column of the worksheet contains the data for the corresponding variable. Each subsequent row contains the data for a specific observation, such as for a person or a company.

Call help(read.table) to view the other R options that can also be implemented from Read.

MECHANICS
Specify the file as with the Read function for reading the data into a data frame. If no arguments are passed to the function, then interactively browse for the file.

Given a csv data file, or tab-delimited text file, read the data into an R data frame called d with Read. Because Read calls the standard R function read.csv, which serves as a wrapper for read.table, the usual options that work with read.table, such as row.names, also can be passed through the call to Read.

SPSS DATA
Relies upon read_spss from the haven package to read data in the SPSS .sav or .zsav format. If the file has a file type of .sav, that is, the file specification ends in .sav, then the format is automatically set to "SPSS". To invoke this option for a relevant data file of any file type, explicitly specify format="SPSS". Each (usually) integer variable with value labels is converted into two R variables: the original numeric code with the original variable name, and also the corresponding factor with the variable labels named with the original name plus the suffix _f. The variable labels are also displayed for copying into a variable label file. See the SPSS section from vignette("Read").

R DATA
Relies upon the standard R function load. By convention only, data files in native R format have a file type of .rda. To read a native R data file, if the file type is .rda, the format is automatically set to "R". To invoke this option for a relevant data file of any file type, explicitly specify format="R". Create a native R data file by saving the current data frame, usually d, with the lessR function Write.

Excel DATA
Relies upon the function read.xlsx from Alexander Walker's openxlsx package. Files with a file type of .xlsx are assigned a format of "Excel". The read.xlsx parameter sheet specifies the ordinal position of the worksheet in the Excel file, with a default value of 1. The row.names parameter can only have a value of 1. Dates stored in Excel as an Excel date type are automatically read as an R Date type. See the help file for read.xlsx for additional parameters, such as sheet for the name or number of the worksheet to read and startRow for the row number for which to start reading data.

lessR DATA
lessR has some data sets included with the package: "BodyMeas", "Cars93", "Employee", "Jackets", "Learn", "Mach4", "Reading", and "StockPrice". Read reads each such data set by specifying its name, such as Read("Employee"). No specificaiton of format and no provided filetype, just enter the name of the data set.

FIXED WIDTH FORMATTED DATA
Relies upon read.fwf. Applies to data files in which the width of the column of data values of a variable is the same for each data value and there is no delimiter to separate adjacent data values_ An example is a data file of Likert scale responses from 1 to 5 on a 50 item survey such that the data consist of 50 columns with no spaces or other delimiter to separate adjacent data values_ To read this data set, invoke the widths option of read.fwf.

MISSING DATA
By default, Read provides a list of each variable and each row with the display of the number of associated missing values, indicated by the standard R missing value code NA. When reading the data, Read automatically sets any empty values as missing. Note that this is different from the R default in read.table in which an empty value for character string variables are treated as a regular data value. Any other valid value for any data type can be set to missing as well with the missing option. To mimic the standard R default for missing character values, set missing=NA.

To not list the variable name or row name of variables or rows without missing data, invoke the miss_zero=FALSE option, which can appreciably reduce the amount of output for large data sets. To view the entire data table in terms of 0's and 1's for non-missing and missing data, respectively, invoke the miss_matrix=TRUE option.

VARIABLE LABELS
Unlike standard R, lessR provides for variable labels, which can be provided for some or all of the variables in a data frame. Store the variable labels in a separate data frame l. The variable labels file that is read by Read consists of one row for each variable for which a variable label is provided. Each row consists of either two columns, the variable name in the first column and the associated variable label in the second column, or three columns with the third column the variable units. Use the units in conjunction for enhanced readability with the automatic markdown generated by the Rmd parameter for the Regression function. The format of the file can be csv or xlsx. The data frame Read constructs from this input consists of one variable, called label, with the variable names as row names.

The lessR legacy approach is to store the variable labels directly with the data in the same data frame. The problem with this approach is that any transformations of the data with any function other than lessR transformation functions remove the variable labels. The option for reading the variable labels with the labels option of Read statement is retained for compatibility.

Reading the data from an SPSS file, however, retains the SPSS variable labels as part of the data file. The lessR data analysis functions will properly process these variable labels, but any non-lessR data transformations will remove the labels from the data frame. To retain the labels, copy them to the l data frame with the VariableLabels function with the name of the data frame as the sole argument.

The lessR functions that provide analysis, such as Histogram for a histogram, automatically include the variable labels in their output, such as the title of a graph. Standard R functions can also use these variable labels by invoking the lessR function label, such as setting main=label(I4) to put the variable label for a variable named I4 in the title of a graph.

Value

The read data frame is returned, usually assigned the name of d as in the examples below. This is the default name for the data frame input into the lessR data analysis functions.

Author(s)

David W. Gerbing (Portland State University; [e-mail])

References

Gerbing, D. W. (2020). R Visualizations: Derive Meaning from Data, Chapter 1, NY: CRC Press.

Alexander Walker (2018). openxlsx: Read, Write and Edit XLSX Files. R package version 4.1.0. https://CRAN.R-project.org/package=openxlsx

See Also

read.csv, read.fwf, corRead, label, details, VariableLabels.

Examples

# remove the # sign before each of the following Read statements to run

# to browse for a data file on the computer system, invoke Read with 
#   the from argument empty
# d <- Read()
# abbreviated name
# d <- rd()

# read the variable labels from
#  the specified label file, here a Excel file with two columns,
#  the first column of variable names and the second column the 
#  corresponding labels
# l <- Read("Employee_lbl", var_labels=TRUE)

# read a csv data file from the web
# d <- Read("http://web.pdx.edu/~gerbing/data/twogroup.csv")

# read a csv data file with -99 and XXX set to missing
# d <- Read(missing=c(-99, "XXX"))

# do not display any output
# d <- Read(quiet=TRUE)
# display full output
# d <- Read(brief=FALSE)

# read the built-in data set dataEmployee
d <- Read("Employee")

# read a data file organized by columns, with a 
#   5 column ID field, 2 column Age field
#   and 75 single columns of data, no spaces between columns
#   name the variables with lessR function: to
#   the variable names are Q01, Q02, ..., Q74, Q75
# d <- Read(widths=c(5,2,rep(1,75)), col.names=c("ID", "Age", to("Q", 75)))

lessR documentation built on June 23, 2024, 1:06 a.m.