3.5 Subsetting / manipulating tibbles

• Extract column by name:

# with the $
mytibble$letters

##  [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V"
## [23] "W" "X" "Y" "Z"

# or the [[]]
mytibble[["letters"]]

##  [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V"
## [23] "W" "X" "Y" "Z"

# Note: with simple square brackets, you extract a sub-tibble (it remains a 2 dimensional object)
mytibble["letters"]

## # A tibble: 26 x 1
##    letters
##    <chr>  
##  1 A      
##  2 B      
##  3 C      
##  4 D      
##  5 E      
##  6 F      
##  7 G      
##  8 H      
##  9 I      
## 10 J      
## # … with 16 more rows

• Extract column by position/index:

# sub-tibble with one column
mytibble[, 1]

## # A tibble: 26 x 1
##    letters
##    <chr>  
##  1 A      
##  2 B      
##  3 C      
##  4 D      
##  5 E      
##  6 F      
##  7 G      
##  8 H      
##  9 I      
## 10 J      
## # … with 16 more rows

# corresponding vector
mytibble[[1]]

##  [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V"
## [23] "W" "X" "Y" "Z"

HANDS-ON

We will work with the built-in dataset iris:

• Is iris a tibble? How can you tell? Try to run is_tibble.
• Convert iris to a tibble. Save in a new object tbl_iris. Run is_tibble on tbl_iris.
• Show all rows of tbl_iris.
• Show the first 3 rows of tbl_iris.
• Extract column Species.

Answer

# Is iris a tibble?
is_tibble(iris)

# Convert iris to a tibble. Save in a new object tbl_iris.
tbl_iris <- tibble(iris)

# Show all rows from tbl_iris.
print(tbl_iris, n=Inf)

# Show the first 3 rows from tbl_iris.
print(tbl_iris, n=3)

# Extract column Species.
  # create a tibble with only one column:
tbl_iris["Species"] 
  # create a vector:
tbl_iris[["Species"]] # same as tbl_iris$Species