Data Frames in R
Data frames are tabular data structures in R, similar to tables in a database or Excel sheets. They are widely used for storing and manipulating structured data.
Creating a Data Frame
Data frames can be created using the data.frame function.
df <- data.frame(
name = c("Alice", "Bob", "Charlie"),
age = c(25, 30, 35),
is_student = c(TRUE, FALSE, TRUE)
)
print(df)
Accessing Data
You can access columns and rows in a data frame using the $ operator and indexing.
# Accessing a Column
print(df$name)
# Accessing a Row
print(df[1, ])
Adding and Removing Columns
You can add or remove columns from a data frame using the $ operator and the NULL assignment.
# Adding a Column
df$salary <- c(50000, 60000, 70000)
# Removing a Column
df$is_student <- NULL
print(df)
Filtering Data
You can filter rows in a data frame using logical conditions.
# Filtering Rows
filtered_df <- df[df$age > 30, ]
print(filtered_df)
Merging Data Frames
You can merge two data frames using the merge function.
df1 <- data.frame(id = c(1, 2, 3), name = c("Alice", "Bob", "Charlie"))
df2 <- data.frame(id = c(1, 2, 4), salary = c(50000, 60000, 70000))
# Merging Data Frames
merged_df <- merge(df1, df2, by = "id")
print(merged_df)
Summarizing Data
You can summarize data using functions like summary and aggregate.
# Summary Statistics
print(summary(df))
# Aggregating Data
print(aggregate(age ~ is_student, data = df, FUN = mean))
Reading and Writing Data
You can read data from and write data to CSV files using read.csv and write.csv.
# Reading from a CSV File
df <- read.csv("data.csv")
# Writing to a CSV File
write.csv(df, "output.csv", row.names = FALSE)