R PROGRAMMING LANGUAGE

Coding standards in R are really important becasue they help you, make your code readable and allow you and other people to understand what's going on in your code. Now, of course, just like it is with any other, style whether it comes, when you, you know, whether it's your clothing or whatever it is, it's difficult to get everyone to agree on one set of ideas. But I think there are a couple of very basic, kind of minimal standards that are important when you're coding in R. Alright, so I'm just going to talk a little bit about some of the coding standards, that I think are important to, when you're writing R code, and I think will help make your code more readable and more usable by others if that's what you're trying to, to achieve.

Play video starting at ::41 and follow transcript

0:41

So, the first principle that I think is very important in pretty much any programming language, not just R, is that you should always write your code using a text editor and save as a text file. Okay, so, a text file is a kind of basic standard. It usually doesn't have any sort of formatting or any sort of, kind of special, appearance, it's just text, right? And usually, typically, typically it's going to be ASCII text, but if you're, on, in places outside the US or the UK using non-English languages there may be other standard text formats. But the basic idea is that a text format, can be read by pretty much any basic editing program. These days, you know, when you're writing something there's a lot different of tools that you can use to write. If you're writing a book, or or a webpage or something like that, there's all kinds of different tools that you can use to write, to write those things. But you're, when you're writing code, you should always try to use a text editor, because that's like kind of like the, the kind of least common denominator, and it makes it so that everyone will be able to access your code and improve upon it.

Play video starting at :1:47 and follow transcript

1:47

The second principle is, which is very important for readability, is to indent your code. So indenting is something that's often hotly debated in lots of mailing lists and other types of discussion groups in terms of how much indenting is appropriate. Now I'm not going to talk about that although I do have some recommendations. But I think the most important thing is that you understand why indenting is important. So indenting is the idea that different blocks of code should be spaced over to the right a little bit more than other blocks of code so you can see kind of how the control flow how the flow of the program goes based on the indenting alone. So coupled with indenting, is the third principle which I think is very simple which is, limit the width of your code. So you have indenting it's possible to kind of indent off to the right forever so you need to limit on the right hand side how wide your code is going to be and usually this is kind of determined by the number of columns of text. And so one possibility is you limit your text to about 80 columns of text and then and so that your, the width of your code never exceeds that. So, let's take a look for, at a quick example here.

Play video starting at :2:53 and follow transcript

2:53

So here you can see I've got R Studio open, here with a simple code file with some R code in it. And, first of all, let me just mention that the editor in R Studio is a text editor. So it will always save the R files that you write as text format files. So, so we've already got that kind of handled. But you can see the indenting scheme here is equal to one space. So every indent is one space. And you can see that all the code is kind of mashed together here on the left hand side. It's difficult to tell kind of where the if blocks are. Where the else blocks are. Where does the function kind of end and begin? And so the indenting scheme kind of makes the code not very readable in this case. So we can change the indenting in R Studio. If we just go up to the Preferences menu here.

Play video starting at :3:36 and follow transcript

3:36

And go to Code Editing. And let me just change it to four. And you can see that the column, the margin column is set to 80 characters, so it will show you the margin when you've reached 80 characters.

Play video starting at :3:46 and follow transcript

3:46

And so I'm going to select all here with Cmd+A, and then Cmd+I to indent it. So now you can see that the indenting is a little bit nicer now. You can see, kind of, where the function begins and ends, you can see where the if blocks start and end, and the, kind of, structure of the program is much more obvious. So, I'm going to change this one more time though and my, because my personal preference for indenting is to use eight spaces, so I'm going to change this to eight.

Play video starting at :4:13 and follow transcript

4:13

Hit OK, and select all. Cmd+I. And now you can see, I prefer the eight spaces just because it really makes the structure of the code very obvious. And the spacing is nice and clear. And it makes the code very readable in general. So you can see that indenting is very important. And the biggest problem you might have is, with the, with, with too little indenting. If you don't indent at all or if you only use a very small amount the code becomes kind of very mashed together. So I recommend at least four spaces for an indent and I'm pref, I prefer, you know, eight spaces for an indent, just because it makes the code much more readable and spaces it out much nice, much more nicely.

Play video starting at :4:52 and follow transcript

4:52

One of the advantages of having something like an eight space indent, is coupled with an 80 character margin on the right hand side, is that it forces you to think about your code in a slightly different way. So for example, if you have eight space indents, if you're going to have a for-loop, nested within another for-loop within another for-loop, every time you nest another for-loop, for example, you have to indent over eight spaces. And by the time you get to maybe your fourth nested for-loop you're pretty much hitting the right hand column at the 80 column margin, right? And so the nice thing about the eight space indent, coupled with the 80 column margin, is that it prevents you from kind of writing very basic, making very kind of fundamental, kind of mistakes with, with code readability. So, for example, with an eight space indent and 80 column margin, you might not be able to do feasibly more than two nested for loops, and, but I think that's really the, kind of, the boundary of what is readable in terms of code. Typically except for some special cases, a three, you know, a three nested or four nested four loop is difficult to read, and it's probably better off, you know, splitting off into separate functions or something like that. So a good indenting policy not only makes the code more readable, but it actually can force you to think about writing your code in a slightly different way. And so that's a really nice advantage of, of having a logical indenting policy with, coupled with a, you know, a right-hand side restriction. Alright. So the last thing I want to talk about is to limit the length of your functions. Alright so, functions in R can, can theoretically go on for quite a long time and of course just like in any other language but just like in any other language I think that the, the logical thing to do with a function is limit it to kind of one basic activity. So for example, if you're function's named read the data. Then your function should simply read the data, it should not read the data, process it, fit a model, and then print some output, alright? So you should, the logical kind of steps like that, should, should probably be spit, split, into separate functions. There are a couple of advantages to doing this. First of all, it's nice to be able to have a function written on a single page of code, so you don't have to scroll endlessly to see, you know, where all the code for this function goes. If you could put all the function, the entire function on like one screen of the editor, then you can look at the whole function and see what it does all at once. Another advantage of splitting up your code into logical sections, to logical functions, is that if you use functions like traceback, or the profiler, or the debugger, these often tell you, you know, where in the function call stack you are when a problem occurs. And if you have multiple functions that are all logically divided in to separate pieces then when a bug occurs and you know that it occurs in a certain type of function or a certain function then you know kind of where to go fix things, right? So if you have, but if just have a single function that just goes on forever and a bug occurs then the only thing that the debugger or the traceback or the profiler can tell you is that there's a problem in this one function. But it, it doesn't, it, it's difficult to tell you where exactly the problem occurs. So splitting up your functions has a secondary benefit, which is that it can help you in debugging and profiling. So limiting the size of your functions is very useful for readability and for, kind of, debugging. Of course, it's easy to go overboard and having, you know, a hundred different three-line functions. So that's not really what you want to do. So you just want to make it so that the, the separation of different functions into, is logical, and that each function kind of does, does one thing in particular.

Play video starting at :8:16 and follow transcript

8:16

So those are my basic guidelines for writing code in R. There are, of course, many other things that you might be able to think about. But then we start bordering into areas that we might, we might kind of disagree on. And so I'm not going to talk about too much more in terms of coding standards, but the basic ideas are always use a text editor, always indent your code, I'd say at least four spaces. Limit on the right hand side how, how wide your code can be.

Play video starting at :8:39 and follow transcript

8:39

And and always limit the size of your functions, so that you can, so that they're, kind of grouped into logical pieces of your program. So with those four things, I think you'll, your, your code will be much more readable. It'll be readable to you, it'll be readable to others, and it'll make kind of writing R code much more useful to everyone.

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