logr 
The logr package helps create log files for R scripts. The package provides easy logging, without the complexity of other logging systems. It is designed for analysts who simply want a written log of the their program execution. The package is implemented as a wrapper to the base R sink() function.
How to use
There are only three logr functions:
log_open()log_print()log_close()
The log_open() function initiates the log. The log_print() function prints an object to the log. The log_close() function closes the log. In normal situations, a user would place the call to log_open() at the top of the program, call log_print() as needed in the program body, and call log_close() once at the end of the program.
A sample program is as follows:
library(logr)
# Create temp file location
tmp <- file.path(tempdir(), "test.log")
# Open log
lf <- log_open(tmp)
# Send message to log
log_print("High Mileage Cars Subset")
# Perform operations
hmc <- subset(mtcars, mtcars$mpg > 20)
# Print data to log
log_print(hmc)
# Close log
log_close()
# View results
writeLines(readLines(lf))
What to print to the log
You can print to the log anything that you can print to the console; vectors, lists, and data frames are all valid objects for logging. Under the hood, logr calls the print() function on that object, and writes the results to the log. The log_print() function, by default, will also print the object to the console. That means you can replace calls to print() with log_print(), and there will be no loss of convenience during development.
What the log looks like
The log created by logr is simpler than most logging packages. This log is designed to be human-readable and increases the traceability of your activities. There are three main enhancements to a logr log:
- A log header
- Notes
- A log footer
Here is an example log, created by the sample program above:
=========================================================================
Log Path: C:/Users/dbosa/AppData/Local/Temp/RtmpQtOzhy/log/test.log
Working Directory: C:/packages/logr
User Name: dbosak
R Version: R Under development (unstable) (2020-06-29 r78751)
Machine: BOSAK-MAIN x86-64
Operating System: Windows 10 x64 build 18362
Log Start Time: 2020-06-30 07:15:52
=========================================================================
High Mileage Cars Subset
NOTE: Log Print Time: 2020-06-30 07:15:52
NOTE: Elapsed Time in seconds: 0.0219531059265137
mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
Datsun 710 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
Merc 240D 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
Merc 230 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
Fiat 128 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
Honda Civic 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
Toyota Corolla 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
Toyota Corona 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
Fiat X1-9 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
Porsche 914-2 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
Lotus Europa 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
Volvo 142E 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2
NOTE: Data frame has 14 rows and 11 columns.
NOTE: Log Print Time: 2020-06-30 07:15:52
NOTE: Elapsed Time in seconds: 0.0508558750152588
=========================================================================
Log End Time: 2020-06-30 07:15:53
Log Elapsed Time: 0 00:00:00
========================================================================= Parts of the log
Log Header
The log header provides an introduction to your log. The header block contains the path of the log file, the working directory, the name of the user, a date-time stamp, and other useful information concerning the operating environment.
Notes
Notes will be written to the log for every call to log_print(). The notes will follow the printing of the object, and will include a date-time stamp and the elapsed time since the last call to log_print(). If the object is of class data.frame the number of rows and columns will also be noted.
Additional Features
Errors and Warnings
logr will write all errors and the last warning to the log. Errors are written at the point they are encountered. Warnings will be written at the end of the log.
Message File *.msg
If errors or warnings are generated, they will also be written to a separate file called a message file. The message file has the same name as the log, but with a .msg extension. The purpose of the message file is so that errors and warnings that occur during execution of the script can be observed from the file system. The presence or absence of the .msg file will indicate whether or not the program ran clean.
Log subdirectory /log
By default, logr prints the log to a subdirectory named log. If that subdirectory does not exist, the log_open() function will create it. The default behavior can be overridden by setting the logdir parameter on the log_open() function to FALSE.