mtcars clearly has row names:
> head(mtcars)
mpg cyl disp hp drat wt qsec vs am gear carb
Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
The documentation for as_tibble tells me that if I set rownames = NA I will get the behavior: NA: keep row names. I tried this:
> as_tibble(mtcars, rownames = NA)
# A tibble: 32 x 11
mpg cyl disp hp drat wt qsec vs am gear carb
* <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
1 21 6 160 110 3.9 2.62 16.5 0 1 4 4
2 21 6 160 110 3.9 2.88 17.0 0 1 4 4
3 22.8 4 108 93 3.85 2.32 18.6 1 1 4 1
4 21.4 6 258 110 3.08 3.22 19.4 1 0 3 1
5 18.7 8 360 175 3.15 3.44 17.0 0 0 3 2
6 18.1 6 225 105 2.76 3.46 20.2 1 0 3 1
7 14.3 8 360 245 3.21 3.57 15.8 0 0 3 4
8 24.4 4 147. 62 3.69 3.19 20 1 0 4 2
9 22.8 4 141. 95 3.92 3.15 22.9 1 0 4 2
10 19.2 6 168. 123 3.92 3.44 18.3 1 0 4 4
# … with 22 more rows
Clearly, the row names are nowhere to be seen. The default behavior, i.e. as_tibble(mtcars,rownames = NULL) (equivalently, as_tibble(mtcars)) produces the same output, but with the asterisk above 1 and to the left of <dbl> removed.
If I instead use the third and final option for rownames, as_tibble(mtcars,rownames = "String here"), I finally get to keep the row names:
> as_tibble(mtcars,rownames = "String here")
# A tibble: 32 x 12
`String here` mpg cyl disp hp drat wt qsec vs am gear carb
<chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
1 Mazda RX4 21 6 160 110 3.9 2.62 16.5 0 1 4 4
2 Mazda RX4 Wag 21 6 160 110 3.9 2.88 17.0 0 1 4 4
3 Datsun 710 22.8 4 108 93 3.85 2.32 18.6 1 1 4 1
4 Hornet 4 Drive 21.4 6 258 110 3.08 3.22 19.4 1 0 3 1
5 Hornet Sportabout 18.7 8 360 175 3.15 3.44 17.0 0 0 3 2
6 Valiant 18.1 6 225 105 2.76 3.46 20.2 1 0 3 1
7 Duster 360 14.3 8 360 245 3.21 3.57 15.8 0 0 3 4
8 Merc 240D 24.4 4 147. 62 3.69 3.19 20 1 0 4 2
9 Merc 230 22.8 4 141. 95 3.92 3.15 22.9 1 0 4 2
10 Merc 280 19.2 6 168. 123 3.92 3.44 18.3 1 0 4 4
# … with 22 more rows
But why was that last step necessary? The documentation says that if I set rownames = NA, then I will get the behavior: NA: keep row names. What about this example prevented rownames = NA from keeping the row names, as the documentation claims that it does?
Using as_tibble(mtcars, rownames = NA) you do keep the rownames, but they are invisible.
library(tidyverse)
as_tibble(mtcars, rownames = NA) %>%
rownames_to_column()
#> # A tibble: 32 x 12
#> rowname mpg cyl disp hp drat wt qsec vs am gear carb
#> <chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 Mazda RX4 21 6 160 110 3.9 2.62 16.5 0 1 4 4
#> 2 Mazda RX4 ~ 21 6 160 110 3.9 2.88 17.0 0 1 4 4
#> 3 Datsun 710 22.8 4 108 93 3.85 2.32 18.6 1 1 4 1
#> 4 Hornet 4 D~ 21.4 6 258 110 3.08 3.22 19.4 1 0 3 1
#> 5 Hornet Spo~ 18.7 8 360 175 3.15 3.44 17.0 0 0 3 2
#> 6 Valiant 18.1 6 225 105 2.76 3.46 20.2 1 0 3 1
#> 7 Duster 360 14.3 8 360 245 3.21 3.57 15.8 0 0 3 4
#> 8 Merc 240D 24.4 4 147. 62 3.69 3.19 20 1 0 4 2
#> 9 Merc 230 22.8 4 141. 95 3.92 3.15 22.9 1 0 4 2
#> 10 Merc 280 19.2 6 168. 123 3.92 3.44 18.3 1 0 4 4
#> # ... with 22 more rows
Check the difference in output for rownames_to_column() when you don't use rownames = NA
as_tibble(mtcars) %>%
rownames_to_column()
#> # A tibble: 32 x 12
#> rowname mpg cyl disp hp drat wt qsec vs am gear carb
#> <chr> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1 1 21 6 160 110 3.9 2.62 16.5 0 1 4 4
#> 2 2 21 6 160 110 3.9 2.88 17.0 0 1 4 4
#> 3 3 22.8 4 108 93 3.85 2.32 18.6 1 1 4 1
#> 4 4 21.4 6 258 110 3.08 3.22 19.4 1 0 3 1
#> 5 5 18.7 8 360 175 3.15 3.44 17.0 0 0 3 2
#> 6 6 18.1 6 225 105 2.76 3.46 20.2 1 0 3 1
#> 7 7 14.3 8 360 245 3.21 3.57 15.8 0 0 3 4
#> 8 8 24.4 4 147. 62 3.69 3.19 20 1 0 4 2
#> 9 9 22.8 4 141. 95 3.92 3.15 22.9 1 0 4 2
#> 10 10 19.2 6 168. 123 3.92 3.44 18.3 1 0 4 4
#> # ... with 22 more rows
Created on 2021-03-02 by the reprex package (v1.0.0)