13.4 Logic of accessing subsets of data frames

  • Same logic as for vectors but two dimensions
    • dataframe[rows,columns]
    • Replace rows/columns by vector indicating position (numerical, logical, character)
  • Logic similar for other object classes such as lists (remember vectors/lists)


# Q: What does the following code do?

swiss[2:4, c(1,2,4)] # indices, c() necessary when numbers are not connected
swiss[swiss$Fertility > 75 & swiss$Agriculture > 75, c(1:3)]
subset(swiss, Fertility > 75 & Agriculture > 75)[, c(1:3)]
swiss[, c("Fertility", "Agriculture")]
# We'll learn a more convenient function later on!