2 L02: Basics I

2.1 Basics of R: Data Structures and Subsetting

2.2 Goals

• Getting to know main data structures in R

2.3 Software{#02}

• R https://www.r-project.org/
• R Studio https://www.rstudio.com/

2.4 Class

• Practice worksheet: 02_worksheets_data-structures.Rmd.zip

NB: Original worksheets prepared by Lincoln Mullen, GMU (https://dh-r.lincolnmullen.com/worksheets.html)

2.5 Topics: Data Structures & Types

• Data structures
  • Vectors
  • Matrices
  • Data frames
  • Lists
• Subsetting operations

2.5.1 Additional notes

• str() compactly dysplays information about an R object
• typeof() determines the internal type or storage mode of an R object
• class() tells you the data structure of an R object:
  • list
  • data.frame
  • matrix
  • vector
    • numeric
      • typeof() > double — a double-precision vector (floats; default numberic vector type)
      • typeof() > integer — a vector of integers
    • character
      • typeof() > character — a vector of strings/characters
• Checking class/type & Conversion
  • create test <- c(1,2,3,4,5)
    • is.___ tests whether a variable of a ___ class.
      • or type: check the typeof() our test vector; then try test.ch <- as.character(test) and check the type again; can you convert it back into its initial type?).
    • is.___ converts into a ___ class.
    • (___ is either: vector, matrix, data.frame, list)
  • Now try the following commands and check the type and class of the new objects:
    • test.matrix <- as.matrix(test)
    • test.df <- as.data.frame(test)
    • test.list <- as.list(test)
    • test.vector <- as.vector(test.df$test)

2.6 Reference materials

• Read two chapters from: Wickham, Hadley. Advanced R, Second Edition. 2 edition. Boca Raton: Chapman and Hall/CRC, 2019. http://adv-r.had.co.nz/
  • Data structures
  • Subsetting
• For the next class, read the following article (in open access, simply follow the link):
  • Broman, Karl W., and Kara H. Woo. 2018. “Data Organization in Spreadsheets.” The American Statistician 72 (1): 2–10. https://doi.org/10.1080/00031305.2017.1375989.
• Additional readings:
  • Read Introduction to Lincoln A. Mullen, Computational Historical Thinking: With Applications in R (2018–): (http://dh-r.lincolnmullen.com/introduction.html)

2.7 Homework

• Finish your worksheet and submit your HW as described below.

2.8 Submitting homework

• Homework assignment must be submitted by the beginning of the next class;
• Email your homework to the instructor as attachments.
  • In the subject of your email, please, add the following: 070184-LXX-HW-YourLastName-YourMatriculationNumber, where LXX is the numnber of the lesson for which you submit homework; YourLastName is your last name; and YourMatriculationNumber is your matriculation number.