Vector Declarations in R
Vectors are fundamental data structures in R that store elements of the same type. Here’s an in-depth look at how to declare and create vectors in R.
Creating Numeric Vectors
Numeric vectors contain numbers.
Example:
# Creating an integer numeric vector num_vec_int <- c(1, 2, 3, 4, 5) # Creating a floating-point numeric vector num_vec_float <- c(1.1, 2.2, 3.3, 4.4, 5.5)
Notes:
- Numeric vectors can contain either integers (1, 2, 3) or floating-point numbers (1.1, 2.2).
- R automatically converts integers to floating-point numbers if necessary to maintain type consistency.
Creating Character Vectors
Character vectors store text strings.
Example:
# Creating a character vector
char_vec <- c("apple", "banana", "cherry")
# Mixing text strings with numbers
char_mixed <- c("Age: ", 25)
Notes:
- If a vector contains characters and numbers, R converts all elements to characters to maintain type consistency.
Creating Logical Vectors
Logical vectors store boolean values: TRUE or FALSE.
Example:
# Creating a logical vector log_vec <- c(TRUE, FALSE, TRUE, FALSE)
Notes:
- Logical vectors are often used for conditions and filtering.
Creating Complex Vectors
Complex vectors can store complex numbers (which have a real and imaginary part).
Example:
# Creating a complex vector comp_vec <- c(1+2i, 3+4i, 5+6i)
Notes:
- Complex numbers are noted with i for the imaginary part (e.g., 3+4i).
Creating Vectors with Element Names
Element names can be assigned to make vectors more readable.
Example:
# Creating a named vector named_vec <- c(a = 1, b = 2, c = 3) # Accessing an element by name element_b <- named_vec["b"]
Notes:
- Element names allow you to reference vector values by names rather than numeric indices.
Creating Vectors with the vector() Function
The vector() function allows you to create vectors of specific types with an initial length.
Example:
# Creating a numeric vector of length 5
vec_numeric <- vector("numeric", length = 5)
# Creating a logical vector of length 3
vec_logical <- vector("logical", length = 3)
Notes:
- vector(“numeric”, length = n) creates a numeric vector of length n with initial values set to 0.
- vector(“logical”, length = n) creates a logical vector of length n with initial values set to FALSE.
Using the c() Function to Combine Vectors
The c() function can also be used to concatenate multiple vectors into a single vector.
Example:
# Creating two vectors vec1 <- c(1, 2, 3) vec2 <- c(4, 5, 6) # Combining the two vectors combined_vec <- c(vec1, vec2)
Notes:
- The c() function concatenates multiple vectors into a single vector.
Using the seq() Function to Create Sequential Vectors
The seq() function generates sequences of numbers.
Example:
# Creating a sequence from 1 to 10 with a step of 1 seq_vec <- seq(1, 10, by = 1) # Creating a sequence with a specific length seq_len_vec <- seq_len(5) # Equivalent to seq(1, 5)
Notes:
- seq(from, to, by) allows you to specify the start, end, and step of the sequence.
- seq_len(n) generates a sequence from 1 to n.
Using the rep() Function to Repeat Elements
The rep() function allows you to repeat elements of a vector.
Example:
# Repeating each element of c(1, 2) twice repeated_vec <- rep(c(1, 2), each = 2) # Repeating the vector c(1, 2) three times repeated_vec_times <- rep(c(1, 2), times = 3)
Notes:
- rep(x, each = n) repeats each element n times.
- rep(x, times = n) repeats the entire vector n times.
Creating Zero-Length Vectors
Vectors can also be created with zero length, which can be useful for subsequent operations.
Example:
# Creating an empty vector empty_vec <- c() # Checking the length of the vector length(empty_vec) # Result: 0
Notes:
- Empty vectors are often used as a base to conditionally add elements later.