In the previous chapter, we explored how to select single rows and columns using basic indexing. Now, we’ll go a step further and learn how to select multiple rows and columns using both base R and the dplyr package. These techniques are essential when you want to focus on specific parts of a dataset or prepare your data for further analysis.

Selecting multiple columns (Base R)

• Use the c() function to combine multiple column positions or names;

• This allows you to select several columns at once;

• The result is a smaller data frame with only the specified columns.

Example using column positions:

selected_data_base <- df[, c(1, 2, 3)]
head(selected_data_base)

Example using column names:

selected_data_base <- df[, c("name", "selling_price", "transmission")]
head(selected_data_base)

Indexing single values

• You can access a specific value using row and column numbers;

• This is helpful for checking or debugging individual data points.

df[1, 2]  # accesses the value in row 1, column 2

Slicing rows

Sometimes you only want to work with the first few rows, or specific rows by position.

Select first 5 rows: Using base R:

first_5_rows_base <- df[1:5, ]
head(first_5_rows_base)

Using dplyr:

first_5_rows_dplyr <- df %>%
  slice(1:5)
head(first_5_rows_dplyr)