With large data files it can be useful to only download the file if it hasn’t
already been downloaded. One way to do this is to check if the file name exists
in your working directory. If it does then load it, if not then download it. You
can use the list.files() function to get a lit of files and directories in the
working directory and the download.file(url, filename) function to download
the file at a url to a specific filename.
Write a conditional statement that checks if surveys.csv exists in the
working directory, downloads it from
https://ndownloader.figshare.com/files/2292172 using if it is not, loads the file
into a data frame and displays the first few rows using the head()
function.
Make a version of this conditional statement that is a function, where the
name of the file is the first argument and the link for downloading the file
is the second argument. The function should return the resulting data frame.
Add some documentation to the top of the function describing what it does.
Call this function using “species.csv” as the file name and
https://ndownloader.figshare.com/files/3299483 as the link. Print the first
few rows of the resulting data frame using head().