📚 R Collections

Vectors are one-dimensional collections where all elements are of the same data type(numeric, character, logical, etc.). You create them with the c() function, which stands for “combine” or “concatenate.”

Indexing starts at 1 in R, not 0 like many other languages.
Operations on vectors are vectorized, meaning they apply element-wise by default.
Mixing types will coerce all elements to a common type (e.g., numeric + string becomes character).

Vectors

# Numeric vector
nums <- c(1, 2, 3)

# Character vector
words <- c("apple", "banana")

Lists

Lists are versatile containers that can hold elements of different types(numeric, character, logical, vectors, other lists, and more).

Elements can be named, which allows for easy reference using $ syntax.
Lists are useful for grouping related but non-uniform data together, such as model results or configurations.
To access nested elements, you can use double brackets [[ ]] or the $ operator for named items.

myList <- list(name = "Alice", age = 30, scores = c(85, 90, 95))

Matrices

Matrices are two-dimensional data structures where all elements must be of the same type. They are often used for numeric computations, linear algebra, and statistical models.

Created using matrix(), specifying nrow and/or ncol.
Filled column-wise by default; use byrow = TRUE to fill row-wise.
Elements are accessed using two indices: [row, column].

m <- matrix(1:6, nrow = 2, ncol = 3)

Data Frames

Data frames are table-like structures where columns can be of different types(numeric, character, logical, factor, etc.), but each column’s elements share the same type.

Think of them as similar to spreadsheets or SQL tables.
Data frames are the most common way to store datasets in R.
Use str(df) to see the structure, and summary(df) for summary statistics.

df <- data.frame(
  name = c("Alice", "Bob"),
  age = c(30, 25)
)

Accessing Elements

You can access elements using indices, names, or$ for named list/data frame elements.

Vectors and matrices use square brackets [] with numeric indices.
Lists and data frames can use $ for named elements/columns.
In matrices and data frames, [row, column] indexing is used; omit one to get a whole row or column.
Indexing in R starts at 1.

nums[1]        # First element of a vector
myList$name    # Access 'name' from a list
m[1, 2]        # Matrix element in row 1, col 2
df$age         # Column 'age' from data frame

Conversion Between Types

Use conversion functions to change between structures when needed.

as.list(nums)
as.vector(m)
as.data.frame(myList)

Best Practices

Choose the right structure based on data type and use case
Use str() to inspect structures
Prefer data frames for real-world datasets

Menu