Filesystem in R

Things under legendu.net/outdated are outdated technologies that the author does not plan to update any more. Please look for better alternatives.

** Things under legendu.net/outdated are outdated technologies that the author does not plan to update any more. Please look for better alternatives. **

1. dirname returns the parent folder of a file or directory, and basename return the name (without the parent folder) of the file or directory.

2. Function file.path joins path components into one path. It works similar to paste which concatenates strings to a single one, but it is platform independent. The following code get the full path of the file 1.txt in the current working directory.

file.path(getwd(), '1.txt')

file.path does not handle the leading/trailing forward/backword slash(es) well, but this does not matter as the result is still a valid Linux-style path.

> file.path('C:/Study/','1.txt')
[1] "C:/Study//1.txt"

The author of this blog has a package named dclong.fs which contains a function join_path that can handle leading/trailing forward/backword slash(es) nicely.

1. There are many useful functions in R which provide low-level interface to the computer's file and directory system, e.g., file.create, file.exists and dir.create and so on. If a function for manipulating directories is missing, it is probably the same as the function for manipulating files, e.g. function file.rename can also be used to rename a directory.

2. file.info returns the information of files and directories. The "isdir" column of the resulting data frame indicates whether a path stands for a file or a directory. For example,

> file.info('.')
  size isdir mode               mtime               ctime
.    0  TRUE  777 2011-11-07 22:26:38 2011-10-20 17:14:41
                atime exe
. 2011-11-07 22:33:37  no

Notice that file\_test can also be used to check whether a path is a file or a directory. For example,

> file_test('-f',".")
[1] FALSE

1. Often times, one need to use temporary files. tempfile returns a vector of character strings which can be used as names for temporary files. By default the temporary file is created in a temporary directory returned by tempdir. For example (the following results is platform dependent),

> tempdir()
[1] "C:\\Users\\adu\\AppData\\Local\\Temp\\Rtmp55KGaO"
> tempfile('output.txt')
[1] "C:\\Users\\adu\\AppData\\Local
\\Temp\\Rtmp55KGaO\\output.txt122935c"

Excel

1. Write hyper link into excel (using write.xlsx) does not work well. One workaround is to write the same content into a CSV file (using write.csv). The hyper links work when you open the CSV file in Excel. You can then save an Excel copy if really want a Excel spreadsheet.