R Script Syntax

Last Updated 2019-04-23 by Adam Lu TODO: Put operators in a table format?

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Variables

# Assign to a variable
var <- 3
var = 3

Arithmetics

# Arithmetics
num1 + num2
num1 - num2
num1 * num2
num1 / num2

# Compute the exponent of a number
num1 ^ exponent

# Compute the remainder of num1 devided by num2
num1 %% num2

# Missing entries
NA

Relations

# Relational operators
==
!=
<=
>=
<
>

# 
|
&

Vectors

Assume myVec is a vector:

# Create a vector by concatenation
myVec <- c(var1, var2, var3)

# Create a sequence vector
myVec <- seq(from = start, to = end, by = increment)

# Access the nth element of a vector
myVec[n]

# Select all but the nth element of a vector
myVec[-n]

# Access elements of a vector satisfying a condition
myVec[condition]

# Element-wise arithmetics
myVec1 + myVec2
myVec1 - myVec2
myVec1 * myVec2
myVec1 / myVec2

Matrices

# Create matrix from a vector
myMat <- matrix(data = myVec, ncol = 3)
myMat <- matrix(data = myVec, nrow = 2)

# Select the mth row of a matrix
myMat[m,]

# Select the nth column of a matrix
myMat[,n]

# Access the element at the mth row and nth column from a matrix
myMat[m, n]

Data Frames

# Create a data frame from vectors
myDf <- data.frame(var1 = vec1, var2 = vec2, var3 = vec3)

# Select a column from a data frame
var1 <- myDf$var1
var1 <- myDf[["var1"]]

Expressions

# Create an expression
myExpr <- expression(var1 ~ var2)

Strings

# Create a string
myStr <- "Beenhakker"

Lists

Assume myList is a list:

# Create list from variables (do not have to be the same length)
myList <- list(name1 = value1, name2 = value2, name3 = value3)

# Access a value for a name-value pair from a list
value1 <- myList$name1
value1 <- myList[["name1"]]

# Create list from variable arguments
args <- myList(...)

Function definitions

# Anonymous functions
function (x) {...}
function (x) {x + 1}			# adds 1 to the first argument

# Define a function called myFun1
# 	Note: arg1 is required
#		  arg2 is optional with a default defined
#		  ... (ellipses) are variable extra arguments
#	      The last output is returned
myFun1 <- function(arg1, arg2 = arg2Default, ...) {
    # Blah
    return(output)
}

# Define a function called myFun2
# 	Note: ... means there can be an indefinite number of arguments
#		  All arguments after ellipses must have default values
myFun2 <- function(..., arg1 = arg1Default) {
    # Blah
}

Binary Operators

# Define a binary operator
"%myBinOp%" <- function(arg1, arg2) {
    # Blah
}

# Use a binary operator
result <- first %myBinOp% second %myBinOp% third

Conditionals

# If else
if {
    # Blah
} else {
    # Bleh
}

# In one line
if (test_expression) "statement1" else "statement2"

Loops

# For loops
for (i in 1:5) {
    # Blah
}

for (item in list) {
    # Blah
}