R-LadiesAbuja - Data Manipulation with data.table in R

March 19, 2022

Learning Objectives:

• How to install data.table package
• How to load the data.tablepackage
• Assessing the structure of a data.table object
  • Printing data.table objects
  • Use head() and tail() to view the first (and last) five rows
  • Use View() to view an entire data.table object
  • Use str() to view the structure of data.table object
  • Use tables() to show all loaded data.table objects
• Sorting and ordering rows using setorder() and order()
• How to remove information:
  • Selecting rows: DT[i,j, by]
  • Selecting rows based on a condition satisfied by column(s)
  • Selecting rows using helper functions: %like% and %between%
  • Selecting columns: DT[i, j, by]
  • Renaming columns
• How to add information:
  • Making new columns while preserving the existing ones using :=
  • Making new columns while dropping existing ones
• How to reduce information:
  • Summarising rows: DT[i, j, by]
  • Grouping by one or more variables
• How to combine information:
  • Joining two data.table objects using merge() and data.table syntax
  • Full join; Inner join; Left join; Right join