R: Recipes for Analysis, Visualization and Machine Learning

Extracting a subset of a dataset

In this recipe, we discuss two ways to subset data. The first approach uses the row and column indices/names, and the other uses the subset() function.

Getting ready

Download the files for this chapter and store the auto-mpg.csv file in your R working directory. Read the data using the following command:

> auto <- read.csv("auto-mpg.csv", stringsAsFactors=FALSE)

The same subsetting principles apply for vectors, lists, arrays, matrices, and data frames. We illustrate with data frames.

How to do it...

The following steps extract a subset of a dataset:

1. Index by position. Get model_year and car_name for the first three cars:

   > auto[1:3, 8:9]
   > auto[1:3, c(8,9)]

2. Index by name. Get model_year and car_name for the first three ...