Introduction to R Programming

rbind() & cbind()

Make sure each dataset has the same variables, same class, and is in the same order.

Merge()

# merge two data frames by variable ID
merge(A, B, by = "ID")

# merge two data frames by variables ID and Country
merge(A, B, by = c("ID". "Country"))  # The default is to use all variables shared by X and Y

#merge two data frames by adding all observations from dataset A
merge(A, B, by = "ID", all.x = TRUE)

#merge two data frames by adding all observations from both datasets
merge(A, B, by = "ID", all = TRUE)

The University of Michigan has provided a great overview — SQL in R

Basics

• SELECT clause: Used to filter observations.
• *: Selects all variables and observations in the selected dataset.
• WHERE clause: Used to filter observations based on specific conditions.
• LIKE with '%': Retrieves records where variables start or end with a specific character.
• LIMIT: A clause used to keep the first 'k' observations.
• GROUP BY: Used to rearrange and group the new dataset by one or several variables.

Commonly Used functions in "dplyr" Package

• filter(): Use this function to select observations by their values.
• mutate(): Create new variables with functions of existing variables.
• select(): Pick variables by their name.
• group_by(): Use this function with the summarize() function to get descriptive statistics.
• summarize(): Obtain requested summary statistics.
• arrange(): Reorder the rows.
• %>%: This operator, also known as the pipe operator, allows you to connect several functions in a sequence.