Data Frames in R

Introduction

Data frames are the most important data structure for data analysis in R. They are like spreadsheets or SQL tables with rows and columns.

Creating Data Frames

# Using data.frame()
df <- data.frame(
  name = c("Alice", "Bob", "Charlie"),
  age = c(25, 30, 35),
  score = c(85, 90, 78)
)

# Using data.frame with stringsAsFactors
df <- data.frame(
  name = c("Alice", "Bob", "Charlie"),
  age = c(25, 30, 35),
  stringsAsFactors = FALSE
)

# Using tibble (tidyverse)
library(tibble)
df <- tibble(
  name = c("Alice", "Bob", "Charlie"),
  age = c(25, 30, 35)
)

Accessing Data Frame Elements

df <- data.frame(
  name = c("Alice", "Bob", "Charlie"),
  age = c(25, 30, 35)
)

df$name         # Column by name
df[, "name"]    # Column selection
df[1, ]         # First row
df[1, 1]        # First cell
df[1:2, ]       # First two rows

Data Frame Functions

df <- data.frame(
  name = c("Alice", "Bob", "Charlie"),
  age = c(25, 30, 35)
)

nrow(df)        # Number of rows
ncol(df)        # Number of columns
dim(df)         # Dimensions
str(df)         # Structure
summary(df)     # Summary statistics
head(df)        # First few rows
tail(df)        # Last few rows
names(df)       # Column names

Modifying Data Frames

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

# Add new column
df$city <- c("NY", "LA")

# Add new row
df <- rbind(df, data.frame(name = "David", age = 28, city = "DC"))

# Remove column
df$city <- NULL

Summary

Data frames are the workhorse of data analysis in R. Master these operations to efficiently work with data.