Video Notes

Multi-Dimensional Data Structures

For two or more dimensions, R provides matrices, arrays, lists, and data frames.

Of these, data frames are the most common and useful for working with datasets.

A data frame is a two-dimensional table-like structure where:

• Each column is a vector
• All columns are the same length
• Columns can hold different data types (numeric, character, logical, etc.)

Example:

results <- data.frame(
  id = 1:3,
  name = c("Alice", "Bob", "Charlie"),
  score = c(85.5, 92.0, 88.5)
)

You can access columns from a data frame using the list extraction operator ($):

results$name # print(my_data$name) # [1] "Alice" "Bob" "Charlie"
mean(results$score) # 88.66667

Exploring Data Frames

Here are some helpful functions for inspecting a data frame:

print(my_data)  # Prints the full data frame
str(my_data)    # Compact summary of structure, types, and sample values
head(my_data)   # First 6 rows
tail(my_data)   # Last 6 rows

In Summary

Data types define what kind of data you have.

Data structures define how that data is organized.

Together, they form the foundation for everything you’ll do in R.