R for Data Science: Tibbles

library("tidyverse")

Loading tidyverse: ggplot2
Loading tidyverse: tibble
Loading tidyverse: tidyr
Loading tidyverse: readr
Loading tidyverse: purrr
Loading tidyverse: dplyr
Conflicts with tidy packages ------------------------------------------------------------------------------------
filter(): dplyr, stats
lag():    dplyr, stats

How can you tell if an object is a tibble? (Hint: try printing mtcars, which is a regular data frame).

On print, a tibble only show the first 10 rows and the columnt types as well.

tb_iris <- as_tibble(iris)
print(tb_iris)

Compare and contrast the following operations on a data.frame and equivalent tibble. What is different? Why might the default data frame behaviours cause you frustration?

df <- data.frame(abc = 1, xyz = "a")
# Notice: No warning on missing column!
df$x

[1] a
Levels: a

# Returning a factor
class(df[, "xyz"])

[1] "factor"

# Returning a data frame
class(df[, c("abc", "xyz")])

[1] "data.frame"

tb_df <- as_tibble(df)
# Notice: Shows warning on missing column!
tb_df$x

Unknown or uninitialised column: 'x'.

NULL

# Returning a tibble
class(tb_df[, "xyz"])

[1] "tbl_df"     "tbl"        "data.frame"

# Returning a tibble
class(tb_df[, c("abc", "xyz")])

[1] "tbl_df"     "tbl"        "data.frame"

If you have the name of a variable stored in an object, e.g. var <- “mpg”, how can you extract the reference variable from a tibble?

tb_cars <- as_tibble(mtcars)
var <- "mpg"
tb_cars[var]

mtcars[var]

Practice referring to non-syntactic names in the following data frame by:

annoying <- tibble(
  `1` = 1:10,
  `2` = `1` * 2 + rnorm(length(`1`))
)

Extracting the variable called 1.

annoying$`1`

 [1]  1  2  3  4  5  6  7  8  9 10

Plotting a scatterplot of 1 vs 2.

ggplot(data = annoying) +
  geom_point(aes(x = `1`, y = `2`))

Creating a new column called 3 which is 2 divided by 1.

mutate(annoying, `3` = `2` / `1`)

Renaming the columns to one, two and three.

transmute(annoying, one = `1`, two = `2`, three = `3`)

What does tibble::enframe() do? When might you use it?

# Converting atomic vectors to data frames, and vice versa
# For backwards compatibility with data frames
help(enframe)

What option controls how many additional column names are printed at the footer of a tibble?

# tibble.max_extra_cols
# Number of extra columns printed in reduced form. Default: 100.
package?tibble