So there are a variety of ways that you can interface between R, R, wi, with the outside world. And generally speaking there are functions that, that are used to kind of open up the what are called connections to the outside world. Usually you want to, the most common type of connection is to me, is to a file, so for example if you want to read a file then you can, you can create a file connection, you might want to for example o, or read a compressed file, or that's a slight variation on that. And most functions will do this in the background without you having to know what's going on. So for example, when you call read.table with it and you pass it the name of a file, what it does behind the scenes is it opens up a file connection to that file, and then reads from that file connection. The connection can be made to other types of objects too. For example, you can open a connection to a webpage using the URL function. And so, when you open a connection to a webpage, you can read data from that webpage using the URL connection. And so, the idea behind the connection interface is, is that it kind of, that it abstracts out. The mechanism for connecting to different types of objects that are external to R, whether they be files, or webpages, or whatever. So the file function is the function that opens a connection to a standard uncompressed file. So this, this can be useful for text files, for, for reading in other types of text files. Gzfile and bzfile, are used for opening connections to compressed data files. So gz file i, are, is used for files that are compressed with the gzip algorithm and bz files used for, is for opening connections to files compressed with the bzip2 algorithm. Files that are compressed with gzip usually have a gz extension and files compressed with bzip2 usually have a bz2 extension. So the file function here has a few arguments, the description argument is the name of the file and there's a flag that's called, that goes to the open argument and you have to know what the codes are, but basically r is for reading, w is for writing, a is for appending, and then rb, wb and ab are for reading, writing, and appending on binary files. The other options for file are not particularly important at this time. So, connections can be very powerful and they can let you navigate files and other external objects in a more sophisticated way than just, like, reading the whole thing, for example. And generally you don't have to deal with the connect interface in many cases, but sometimes it's useful. So for example, so here I've got a simple example or opening a fi, a file connection to some file called foo.text, I'm going to open it for reading. I can call read.csv on the connection, and that by default will just read the entire file then I can close the connection. So that three line process is the same as just calling read.csv on the file. So in this case there was no need to use the connection to read the file. However, sometimes a connection can be useful if you want to read parts of a file. So for example, here I've got the readLines function which just reads lines from a text file. And I'm going to open up this words.gz file. So, this is a file that has words in it for it's like a dictionary file. And it's compressed using the gz, the gzip algorithm. So I'm going to be using the gz file function to open a connection to that. And I'm just going to read the first ten lines. So now I'm going to re, use this connection, and to read the first ten lines. And here, the first ten lines are printed out here as you can see these are the first top ten words in the file. And similarly, write lines is a, is a function that can be used to write out lines of text to a file. And each, and what you do is pass write lines of character vector and each element of the character vector becomes a line in the text file. You can also use readLines to read elements from a web page, so for example, you can use the URL function to create a connection to a website, so this website here is the Johns Hopkins School of Public Health website. And I'm going to open the connection there for reading, and then I'm going to read lines from this connection. And so and I'm, and then and so the lines of text that come from the connection are going to be stored in this character vector x. So when I look at the first couple of lines from x you can see that it looks like HTML which is kind of what you would expect. And so the URL function is useful for creating a connection to a kind of a non file object. and then using read.lines is useful to read the text from that connection. So this is another way to read data beyond using functions like read.table or read.csv
