Intro to Data Frames in R

Review

• Which data structures have we learned so far?
  • Vector:
    • Atomic Vector
    • List
  • Matrix
  • Array

Data Frames

• Data frames are the two-dimensional version of a list.
• Store data in a table format, like an Excel spreadsheet.

faithful

• Data frames group vectors together into a two-dimensional table.
• Each vector becomes a column in the table. Hence, every column must be of the same length.
• Each column of a data frame can contain a different type of data.
• But within a column, every cell must be of the same type of data.

A data frame is a list of vectors of the same length.

Creating a Data Frame

• Use data.frame() function to creata a data frame by hand:

cards <- data.frame(face = c("ace", "two", "six"),
                    suit = c("clubs", "clubs", "clubs"),
                    value = c(1, 2, 3))
cards

• The str() function show what types of objects are grouped together in the data frame.

str(cards)

## 'data.frame':    3 obs. of  3 variables:
##  $ face : Factor w/ 3 levels "ace","six","two": 1 3 2
##  $ suit : Factor w/ 1 level "clubs": 1 1 1
##  $ value: num  1 2 3

Loading Data

Using RStudio Interface

• Download the file deck.csv to your computer.
  • CSV is short for comma-separated values file.
• We will first learn how to load data through the RStudio interface.