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Selection: 2
| | 0%
| In this lesson, you'll learn how to examine your local workspace in R and
| begin to explore the relationship between your workspace and the file system
| of your machine.
|== | 2%
| Because different operating systems have different conventions with regards
| to things like file paths, the outputs of these commands may vary across
| machines.
...
|=== | 5%
| However it's important to note that R provides a common API (a common set of
| commands) for interacting with files, that way your code will work across
| different kinds of computers.
...
|===== | 7%
| Let's jump right in so you can get a feel for how these special functions
| work!
|======= | 10%
| Determine which directory your R session is using as its current working
| directory using getwd().
> getwd()
[1] "D:/Users/sibythom/Documents"
| Perseverance, that's the answer.
|======== | 12%
| List all the objects in your local workspace using ls().
> ls()
[1] "my_div" "my_sqrt" "x" "y" "z"
| Keep working like that and you'll get there!
|========== | 14%
| Some R commands are the same as their equivalents commands on Linux or on a
| Mac. Both Linux and Mac operating systems are based on an operating system
| called Unix. It's always a good idea to learn more about Unix!
...
|============ | 17%
| Assign 9 to x using x <- 9.
> x<-9
| All that practice is paying off!
|
|============= | 19%
| Now take a look at objects that are in your workspace using ls().
> ls()
[1] "my_div" "my_sqrt" "x" "y" "z"
| You are really on a roll!
|=============== | 21%
| List all the files in your working directory using list.files() or dir().
> list.files()
[1] "cache"
[2] "Copy of Shine com overview.xlsx"
[3] "Doc1.docx"
[4] "Employee Form (2).xlsm"
[5] "FW Proposal for 16 more logins.msg"
[6] "key roles (4).xlsm"
[7] "My Meetings"
[8] "My Received Files"
[9] "PMD for the team (2) (Autosaved).xls"
[10] "Project.docx"
| Your dedication is inspiring!
|================= | 24%
| As we go through this lesson, you should be examining the help page for each
| new function. Check out the help page for list.files with the command
| ?list.files.
> ?list.files
| Perseverance, that's the answer.
|================== | 26%
| One of the most helpful parts of any R help file is the See Also section.
| Read that section for list.files. Some of these functions may be used in
| later portions of this lesson.
...
|
|==================== | 29%
| Using the args() function on a function name is also a handy way to see what
| arguments a function can take.
...args()
|
|====================== | 31%
| Use the args() function to determine the arguments to list.files().
>
> args list.files()
Error: unexpected symbol in "args list.files"
> args(list.files)
function (path = ".", pattern = NULL, all.files = FALSE, full.names = FALSE,
recursive = FALSE, ignore.case = FALSE, include.dirs = FALSE,
no.. = FALSE)
NULL
| Nice work!
|
|======================= | 33%
| Assign the value of the current working directory to a variable called
| "old.dir".
> old.dir<-getwd()
| All that hard work is paying off!
|
|========================= | 36%
| We will use old.dir at the end of this lesson to move back to the place that
| we started. A lot of query functions like getwd() have the useful property
| that they return the answer to the question as a result of the function.
...
|
|=========================== | 38%
| Use dir.create() to create a directory in the current working directory
| called "testdir".
> dir.create("testdir")
| Nice work!
|
|============================ | 40%
| We will do all our work in this new directory and then delete it after we are
| done. This is the R analog to "Take only pictures, leave only footprints."
...
|
|============================== | 43%
| Set your working directory to "testdir" with the setwd() command.
> setwd("testdir")
| You are quite good my friend!
|
|================================ | 45%
| In general, you will want your working directory to be someplace sensible,
| perhaps created for the specific project that you are working on. In fact,
| organizing your work in R packages using RStudio is an excellent option.
| Check out RStudio at http://www.rstudio.com/
...
|
|================================= | 48%
| Create a file in your working directory called "mytest.R" using the
| file.create() function.
> file.create("mytest.R")
[1] TRUE
| You got it right!
|
|=================================== | 50%
| This should be the only file in this newly created directory. Let's check
| this by listing all the files in the current directory.
> list.files()
[1] "mytest.R"
| You are quite good my friend!
|
|===================================== | 52%
| Check to see if "mytest.R" exists in the working directory using the
| file.exists() function.
> file.exists()
Error in file.exists() : invalid 'file' argument
> file.exists("mytest.R")
[1] TRUE
| You got it!
|
|====================================== | 55%
| These sorts of functions are excessive for interactive use. But, if you are
| running a program that loops through a series of files and does some
| processing on each one, you will want to check to see that each exists before
| you try to process it.
...
|
|======================================== | 57%
| Access information about the file "mytest.R" by using file.info().
> file.info("mytest.R")
size isdir mode mtime ctime
mytest.R 0 FALSE 666 2016-05-12 23:24:50 2016-05-12 23:24:50
atime exe
mytest.R 2016-05-12 23:24:50 no
| You are quite good my friend!
|
|========================================== | 60%
| You can use the $ operator --- e.g., file.info("mytest.R")$mode --- to grab
| specific items.
...file.info("mytest.R")$mode
|
|=========================================== | 62%
| Change the name of the file "mytest.R" to "mytest2.R" by using file.rename().
> file.rename("mytest2.R")
Error in file.rename("mytest2.R") :
argument "to" is missing, with no default
> file.rename("mytest.R")
Error in file.rename("mytest.R") :
argument "to" is missing, with no default
> file.rename("mytest.R","mytest2.R")
[1] TRUE
| You are amazing!
|
|============================================= | 64%
| Your operating system will provide simpler tools for these sorts of tasks,
| but having the ability to manipulate files programatically is useful. You
| might now try to delete mytest.R using file.remove('mytest.R'), but that
| won't work since mytest.R no longer exists. You have already renamed it.
...
|
|=============================================== | 67%
| Make a copy of "mytest2.R" called "mytest3.R" using file.copy().
> file.copy("mytest2.R","mytest3.R")
[1] TRUE
| That's the answer I was looking for.
|
|================================================ | 69%
| You now have two files in the current directory. That may not seem very
| interesting. But what if you were working with dozens, or millions, of
| individual files? In that case, being able to programatically act on many
| files would be absolutely necessary. Don't forget that you can, temporarily,
| leave the lesson by typing play() and then return by typing nxt().
...play()
|
|================================================== | 71%
| Provide the relative path to the file "mytest3.R" by using file.path().
> nxt()
| Resuming lesson...
| Provide the relative path to the file "mytest3.R" by using file.path().
> file.path("mytest3.R")
[1] "mytest3.R"
| You nailed it! Good job!
|
|==================================================== | 74%
| You can use file.path to construct file and directory paths that are
| independent of the operating system your R code is running on. Pass 'folder1'
| and 'folder2' as arguments to file.path to make a platform-independent
| pathname.
> file.path("folder1","folder2")
[1] "folder1/folder2"
| All that hard work is paying off!
|
|===================================================== | 76%
| Take a look at the documentation for dir.create by entering ?dir.create .
| Notice the 'recursive' argument. In order to create nested directories,
| 'recursive' must be set to TRUE.
> ?dire.create
No documentation for ‘dire.create’ in specified packages and libraries:
you could try ‘??dire.create’
| Not quite, but you're learning! Try again. Or, type info() for more options.
| ?dir.create will show you the docs.
> ?dir.create
| Perseverance, that's the answer.
|
|======================================================= | 79%
| Create a directory in the current working directory called "testdir2" and a
| subdirectory for it called "testdir3", all in one command by using
| dir.create() and file.path().
> dir.create(file.path("testdir2","testdir3"),recursive = TRUE)
| All that hard work is paying off!
|
|========================================================= | 81%
| To delete a directory you need to use the recursive = TRUE argument with the
| function unlink(). If you don't use recursive = TRUE, R is concerned that
| you're unaware that you're deleting a directory and all of its contents. R
| reasons that, if you don't specify that recursive equals TRUE, you don't know
| that something is in the directory you're trying to delete. R tries to
| prevent you from making a mistake.
...
|
|========================================================== | 83%
| Delete the "testdir2" directory that you created by using unlink().
> unlink("testdir2", recursive = TRUE)
| You got it right!
|
|============================================================ | 86%
| Why is this command named "unlink" rather than something more sensible like
| "dir.delete" or "dir.remove"? Mainly, history. unlink is the traditional Unix
| command for removing directories.
...
|
|============================================================== | 88%
| Go back to your original working directory using setwd(). (Recall that we
| created the variable old.dir with the full path for the orginal working
| directory at the start of these questions.)
> setwd(old.dir)
| All that hard work is paying off!
|
|=============================================================== | 90%
| It is often helpful to save the settings that you had before you began an
| analysis and then go back to them at the end. This trick is often used within
| functions; you save, say, the par() settings that you started with, mess
| around a bunch, and then set them back to the original values at the end.
| This isn't the same as what we have done here, but it seems similar enough to
| mention.
...
|
|================================================================= | 93%
| Delete the 'testdir' directory that you just left (and everything in it)
> unlink("testdir", recursive = TRUE)
| You got it!
|=================================================================== | 95%
| Take nothing but results. Leave nothing but assumptions. That sounds like
| 'Take nothing but pictures. Leave nothing but footprints.' But it makes no
| sense! Surely our readers can come up with a better motto . . .
...
|
|==================================================================== | 98%
| In this lesson, you learned how to examine your R workspace and work with the
| file system of your machine from within R. Thanks for playing!
...
|
|======================================================================| 100%
| Would you like to receive credit for completing this course on Coursera.org?
1: No
2: Yes
Selection: 1
| You are doing so well!
| You've reached the end of this lesson! Returning to the main menu...
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