Below are some frequently asked questions about the logr package. Click on the links below to navigate to the full question and answer content.

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Where is my log?

Q: I followed the examples to add logr functions to my script, and I think I created a log. But I can’t find it. Where does the log go?

A: It depends on what you passed to the file_name parameter on the log_open() function.

If you passed nothing, the log will be created in a subdirectory named “log” in the same directory as your program, and with the program name.

If you passed a file name without a path, the log subdirectory will be created in your working directory, and the log will be named with the name you assigned it.

If you passed a full path, it will be created in the full path, but will still be created in a subdirectory named “log” unless the logdir parameter on log_open() is set to FALSE.

If you still can’t find it, add the following line to your program someplace after the call to log_open():

print(log_path())

Then rerun the program. The path to the log will be printed to the console.

Note that the log_open() function also returns the path to the log. You can save this path in a variable for easy access, like this:

pth <- log_open()
print(pth)

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How come it didn’t log anything?

Q: I am able to create a log. But it doesn’t contain anything. Just a header and footer. How come nothing was logged?

A: The logr log is not a fully automatic log, such as a SAS® log. The primary way to get something logged is to log it explicitly with log_print() or put(). This is the only way to guarantee that something will be logged. Generally, if you want a complete log, it is best to sprinkle these functions liberally throughout the program, logging anything you feel is relevant.

The other way to get something to log is by using the autolog feature. This feature can be turned on in one of two ways:
1. Set the autolog parameter on the log_open() function to TRUE.
2. Set the “logr.autolog” option using an options() function, like so:

options("logr.autolog" = TRUE)

The autolog feature will automatically log function calls from the dplyr, tidyr, and the sassy family of packages. It will not log Base R functions, or the functions from any other packages. It takes some experience to understand which functions will be automatically logged, and which will not.

To maximize the autolog feature, it is a best practice to use tidyverse functions, rather than the Base R equivalents. These functions stand a better chance of being logged automatically.

It is also a best practice to place a put() statement at the end of your dplyr pipelines. This is a very good habit to develop, and will greatly improve the quantity and quality of your logs. Here is an example:

dat <- mtcars %>% 
       subset(mpg < 20) %>% 
       arrange(mpg) %>% 
       put()

Note that the above put() statement has no effect on the resulting data frame. It simply logs the pipeline result before assigning it to the variable dat.

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How do I change the name of the log?

Q: I have a log. But I don’t want the default name. How can I change it to something else?

A: The file_name parameter on the log_open() function controls the log name. You can set this parameter to be any log name you like. When the log is created, it will use the name set on this parameter. Example:

log_open("MyCustomName.log")

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How do I add a timestamp to the log name?

Q: I have an R program that runs on a schedule every day. I want to keep the logs from this program for a certain period of time. But logr always overwrites the log from the last run. Is there a way to get a datestamp on the log name, so it won’t overwrite?

A: You can append the datestamp to the log name on the file_name parameter. Like this:

# Concatenate log name with datestamp
nm <- paste0("mylog_", format(Sys.Date(), "%Y-%m-%d"))

# Open log
lf <- log_open(nm)

Then logr will not delete the previous day’s log.

If you want a full date and time stamp, adjust the codes on the format() function to your liking.

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How do I log my code?

Q: In SAS® there is an option to log all the code in my program at the top of the log. I like this because it is a good record of my program at the time it was run. Is there a similar option in logr?

A: There is not an option, but there is a log_code() function that will allow you to accomplish the same thing. You just call the log_code() function at the point where you want the code logged. Normally this would be at the top of the program, after the call to log_open(). Like this:

# Open log
log_open("mylog.log")

# Dump code to log
log_code()

# Continue program...

The above code will dump the entire program contents to the log. The code lines will be prefixed with a right arrow (“>”) to distinguish these lines from the rest of your log.

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How do I turn on symbolgen?

Q: In SAS® there is an option called symbolgen that will log all the variable values in my program. This option is useful for debugging. Is there a similar option in logr?

A: Not really. You can log the values of individual variables by sending them to the log with a put() function. You can also log the entire environment with all variable values like this:

# Open log
log_open("test.log")

# Write current variables to log
put(ls().str())

# Close log
log_close()

Otherwise, it is better to debug R programs interactively. The interactive debugging features in R are much better than in SAS®. The logr log is geared more toward recording the execution of your program than debugging.

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How do I log environment variables and their values?

Q: I want to write all the environment variables and their values to the logr log. Is there a way to do that?

A: There is no built-in feature to log the environment variables. But there is a Base R function Sys.getenv() that will retrieve the environment variables and their values. Then you can put them to the log like any other object:

# Open log
log_open("test.log")

# Send environment variables to log
put(Sys.getenv())

# Close log
log_close()

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How do I turn off the notes?

Q: The notes are cluttering up my log, and are not providing anything that I need. I don’t need the elapsed time, etc. How can I turn them off?

A: The notes can be disabled in one of two ways:
1. Set the show_notes parameter on log_open() to FALSE.
2. Set the logr.notes option to FALSE using an options() function. Like this:

   options("logr.notes" = FALSE)

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How is put() different from log_print()?

Q: There is another function put() that seems similar to log_print(). What is the difference between them?

A: There is no difference in functionality. put() is a direct alias of log_print(). The only difference is that put() is faster to type. It is also easy to remember for anyone who has used SAS® software. The put() function in the logr package does the same thing as the %put() function in SAS®. So this alias will warm the hearts of current/former SAS® programmers.

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What are the “Base Packages” and “Other Packages” lines in the header?

Q: Recently I noticed the “Base Packages” and “Other Packages” lines show up in the log header. What are these lines? Are they supposed to have all my referenced packages? How come some are missing?

A: The “Base Packages” and “Other Packages” lines in the header are attempting to more fully describe the environment the program/script is running in. They are showing the packages that are installed and attached at the point the log_open() function was called.

The information from these lines is taken from Base R sessionInfo(), and shows a subset of information from that function. This information is being logged so that you have some record of the packages and versions that were in use at the time the script was ran. This is useful information if you need to recreate the output from a particular point in time.

Note that if you attach packages in the middle of the program, after the call to log_open(), these packages may not be recorded in the header. It is therefore best practice to place all of your library() calls at the top of your program, load up everything you need, and then call log_open(). This practice will help ensure that the header contains all the packages that are used by your program. This practice also makes your program easier to read, understand, and maintain.

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How come the warnings are at the bottom of the log?

Q: I noticed that errors are logged at the point they are generated. But warnings are only logged at the end of the log file. Why?

A: Base R provides an error event that can be triggered when an error occurs, and therefore the errors can be logged at the point in the program where they are encountered. The corresponding event for warnings does not work (at least on Windows).

If anyone can find a way to trigger the warnings event, please submit an issue to the logr Github issue list and I will add it to the package.

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How come only the last warning is logged?

Q: It appears that only the last warning is logged. But I have a lot of warnings. How come only the last warning is recorded? Is there a way to make it log all of them?

A: The last warning is recorded in the log because only the last warning is stored and can be easily retrieved in Base R. Further, because the warnings event does not trigger properly, dumping all the warnings to the log at the end would make no sense. If anyone can find a better way to trigger and log warnings at the point where the warning is generated, please submit an issue to the logr Github issue list and I will add it to the package.

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