CRAN-R_RefreshPArt10

This post just follows the previews refresh9.

WORKING WITH Data Frames

Data Frame manipulation

Example

# Built-in R data set stored in a data frame

mtcars

head(mtcars)

tail(mtcars)

# Investigate the structure of the mtcars data set to get started!

str(mtcars)

# planets

planets <- c("Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune");

type <- c("Terrestrial planet", "Terrestrial planet", "Terrestrial planet", "Terrestrial planet", "Gas giant", "Gas giant", "Gas giant", "Gas giant")

diameter <- c(0.382, 0.949, 1, 0.532, 11.209, 9.449, 4.007, 3.883); 

rotation <- c(58.64, -243.02, 1, 1.03, 0.41, 0.43, -0.72, 0.67);

rings <- c(FALSE, FALSE, FALSE, FALSE, TRUE, TRUE, TRUE, TRUE);

# Create the data frame:

planets_df  <-data.frame(planets,type,diameter,rotation,rings)

#

order(planets_df)

# Check the structure of 'planets_df'

str(planets_df)

# All data from the first three planets

closest_planets_df <- planets_df[1:3, ]

# All data from the last three planets

furthest_planets_df <- planets_df[6:8, ]

# Do selection on both rows and columns

furthest_planets_diameter <- planets_df[3:8,"diameter"]

# Create the rings_vector

rings_vector <- planets_df[,"rings"]

rings_vector

# Select the information on planets with rings:

planets_with_rings_df <- planets_df[rings_vector,]

# Planets that are smaller than planet Earth:

small_planets_df  <- subset(planets_df, subset = diameter < 1)

# What is the correct ordering based on the planets_df$diameter variable?

positions <- order(planets_df$diameter, decreasing = TRUE)

# Create new "ordered" data frame:

largest_first_df <- planets_df[positions, ]