R Course

Learn basics in 5 minutes

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You will learn the most basic things you need to know to write some code. You may need to check the files/plots functions later if you are planning to do some statistics.


Variables

You can assign a variable x to a value 5 using <-.

x <- 5

Expressions

You can do comments with #. You may or not add a ; at the end of a line.

If a line is evaluated to be a value then R will print it. For example, when I do x <- 5 I assign something so that's not a value. But if I write x or "test" it's a value so R will print it.

# will print 5
x
# explicit call to print
print("test")

Functions

You can write a function using the keyword function. Parameters can have a default value and they can be passed in whatever order you want if you use named arguments.

my_function <- function (x, y=2){
  return(x + y)
}

my_function(5) # y = 2
my_function(y=3, x=5) # use names

Statements

Aside from if and for i in (explained later), you won't use and should not use any structure.

if ( condition ) {
    // ...
}

Vectors

In R, all values are a vector. In fact 5 is considered as a vector of size 1. A vector is like an array, but when you do something like vector * 2 or function(vector) then the operation is applied (or most likely will, in case of functions, since that's up to the one coding) to every element of a vector.

# shortcut to create a vector from [[1,10]]
one_to_ten <- 1:10
# get first value (INDEXES START AT 1)
one_to_ten[1] # print 1
one_to_ten[length(one_to_ten)] # print 10

# for i in
# print 1 then 2 ...
for (i in one_to_ten) { print(i) }

# In R, it's preffered that you use the "apply"
# function instead of a loop
sapply(one_to_ten, function (i) { print(i) } )

R is guessing the type of a variable but you can use a constructor to explicitly create a variable having a type.

# create a vector of 10 numerics (=float or int) values
numeric(10)