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Control Structures - If-else

Course video 30 of 55

Welcome to Week 2 of R Programming. This week, we take the gloves off, and the lectures cover key topics like control structures and functions. We also introduce the first programming assignment for the course, which is due at the end of the week.

Linguagem R

Universidade Johns Hopkins

Curso 2 de 10 no Ciência de Dados Programa de cursos integrados

In this course you will learn how to program in R and how to use R for effective data analysis. You will learn how to install and configure software necessary for a statistical programming environment and describe generic programming language concepts as they are implemented in a high-level statistical language. The course covers practical issues in statistical computing which includes programming in R, reading data into R, accessing R packages, writing R functions, debugging, profiling R code, and organizing and commenting R code. Topics in statistical data analysis will provide working examples.

Visualizar o programa do curso

Habilidades que você aprenderá

Data Analysis, Debugging, R Programming, Rstudio

Ministrado por

Roger D. Peng, PhD
Associate Professor, Biostatistics
Jeff Leek, PhD
Associate Professor, Biostatistics
Brian Caffo, PhD
Professor, Biostatistics

Transcrição

So the first structure is if, so this is a, this, the, the if combined with else

allows you to test logic conditions, and to let the r program do something, give,

whether or not, depending on whether that conditions is true or false.

So if the condition is true then you do something else you do something else.

That's the typical kind of construct.

The else part is optional, so

you could just have an if statement to do something if something is true.

But you can have the else part if you wanted to do something alternatively.

If you want to do more, there's more than one possible type of condition you

can tick, you, you want to check.

You can say if, and then, else, if and then, else.

else, if there can be any number of else,

if conditions in a constraint like this and the else one has to be at the end.

So there are a couple of different ways that you can formulate the if else

construct in r, it's a little, this is a little bit different from other languages.

Case you haven't seen something like this.

So the first is pretty standard if x, if the con,

if sorry if the symbol x is greater than 3 then you select, you set y equal to 10.

If it's not greater than 3 then you set y equal to 0.

So that's inside the if-else construct, there's, there's an assignment of y

to a specific type of value depending on what the value of 3, of x if.

But however in r you can do it a different way you can say y is

equal to the entire if else construct.

So if x is greater than 3, 10 or

0 depending on whether that conditions true or not.

So this is a valid formulation also.

Sometimes it's, it's,

it's useful to read this type of writing because it, it allows you to

realize that the entire if else construct is all about assigning a value to y.

So as I said before the else clause is not really necessary you can

always test the condition and

do something and then do nothing if that condition happens to be false.

So you can and you can just test multiple conditions in a row if you want

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