R Cookbook, 2nd Edition

Chapter 12. Useful Tricks

The recipes in this chapter are neither obscure numerical calculations nor deep statistical techniques. Yet they are useful functions and idioms that you will likely need at one time or another.

12.1 Peeking at Your Data

Problem

You have a lot of data—too much to display at once. Nonetheless, you want to see some of the data.

Solution

Use head to view the first few data values or rows:

head(x)

Use tail to view the last few data values or rows:

tail(x)

Or you can view the whole thing in an interactive viewer in RStudio:

View(x)

Discussion

Printing a large dataset is pointless because everything just rolls off your screen. Use head to see a little bit of the data (six rows by default):

load(file = './data/lab_df.rdata')
head(lab_df)
#>         x lab      y
#> 1  0.0761  NJ  1.621
#> 2  1.4149  KY 10.338
#> 3  2.5176  KY 14.284
#> 4 -0.3043  KY  0.599
#> 5  2.3916  KY 13.091
#> 6  2.0602  NJ 16.321

Use tail to see the last few rows and the number of rows:

tail(lab_df)
#>          x lab      y
#> 195  7.353  KY 38.880
#> 196 -0.742  KY -0.298
#> 197  2.116  NJ 11.629
#> 198  1.606  KY  9.408
#> 199 -0.523  KY -1.089
#> 200  0.675  KY  5.808

Both head and tail allow you to pass a number to the function to set the number of rows returned:

tail(lab_df, 2)
#>          x lab     y
#> 199 -0.523  KY -1.09
#> 200  0.675  KY  5.81

RStudio comes with an interactive viewer built in. You can call the viewer from the console or a script:

View(lab_df)

Or you can pipe an object to the viewer:

lab_df %>%
  View()

When piping to