Declaring Variables in R

Question

I am new to the world of R Programming and when I tried declaring variables in R I couldn't find any specific way which exists In other Programming languages like C which expects a variable to be declared before using it, Though in vba we can define variables without defining it, which is assumed to be a special variant, but we can use a Special Statement called Option Explicit which does not allows us not to use the undeclared variables.

Though it is convenient way but in large Programs one can easily commit typo errors which may be extremely hard to find so my question is, In R Programming is there any such Option/Utility Exists to make the variables declared before it is defined?

In C language a variable declared as int type can hold an integer value only, a char type identifier can hold character value only etc. In R language, suppose currently an identifier assigned a vector. At a later time point, we use the same identifier to hold a list or a data.frame or a matrix. — Lella
– Lella, Commented Sep 2, 2017 at 5:25
Hi Rao, thank you for your response, yes I agree that we can type cast the variables during data cleaning and data modeling process but can't we do a formal declaration in r, because in vb we used to use a special statement called Option ("Explicit") in order to declare the variables formally so that we can prevent the redefining the variables and typo errors etc. — shivanesh
– shivanesh, Commented Sep 2, 2017 at 7:10

PraneetNigam · Accepted Answer · 2017-09-02 11:49:27Z

7

The core of R is an interpreted computer language. Which help it in declaring the variable anytime. Which is an advantage over C language where you need to declare the variables initially...But as you said "for a small programs it will be fine to define variables without declaring it initially but for a large programs we can easily commit errors by redefining the variable again".. So to overcome from this problem I have a solution....You can check every time before defining a new variable that whether it's already defined previously or not. And how you can do that see below: You can use the help of function exists()

> a <- 6
> exists("a")
[1] TRUE
> exists("b")
[1] FALSE

You can easily check whether the variable you have previously defined or not..

answered Sep 2, 2017 at 11:49

PraneetNigam

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Tim Biegeleisen · Accepted Answer · 2017-09-02 04:09:34Z

5

In R it is not necessary to do a formal declaration of a variable as you would need to do in a language like Java or C#. Rather, the variable will get its type from the right hand side of the assignment. That being said, if you need to declare a variable as having a type, you could assign it to a zero length object of the type you want, e.g.

x <- character()
class(x)
[1] "character"
length(x)
[1] 0
y <- numeric()
class(y)
[1] "numeric"
length(y)
[1] 0

One instance where you might need to assign the type of a variable would be if you needed an empty data frame but with known column types.

edited Sep 2, 2017 at 4:09

answered Sep 2, 2017 at 4:04

Tim Biegeleisen

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2 Comments

shivanesh Over a year ago

Thank you for your Response Tim, for a small programs it will be fine to define variables without declaring but for a large programs we can easily commit errors by redefining the variable again, so if we declare it we may not commit such errors so is there a explicit way to tell R to declare variables before defining it?

www Over a year ago

This gives useful information. It's not incorrect, but overall, it could be somewhat misleading for users that might not know as much about R. Making something a certain class in R isn't the same as the way we might declare and apply constraints to an object in C. Since the OP was asking for functionality similar to that found in C, it would be most helpful to clarify those differences. See L.V.Rao's comment to shivanesh for another explanation/source.

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