What does a star above row numbers in a tibble mean?

[davidhodge931]

[DavoWW]

Hi @davidhodge931,
The star means that the tibble has row names (which are not displayed). Row names are normally dropped when making a tibble (better to have the data in a true column). See differences here using the mtcars in-built dataframe which has row names:

suppressPackageStartupMessages(library(tidyverse))
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
rownames(head(mtcars))
#> [1] "Mazda RX4"         "Mazda RX4 Wag"     "Datsun 710"       
#> [4] "Hornet 4 Drive"    "Hornet Sportabout" "Valiant"

as_tibble(head(mtcars))
#> # A tibble: 6 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

as_tibble(head(mtcars), rownames=NA)
#> # A tibble: 6 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

^{Created on 2021-09-10 by the reprex package (v2.0.1)}

[acullum]

I'm trying not to be an idiot here, but I'm a little confused. You say "The star means that the tibble has row names", but in your example the case with the row names intact does not have an asterisk, but the case with the row names removed does have an asterisk. Isn't that the opposite of what your explanation?

[EconProf]

The first case is a plain dataframe, not a tibble. A dataframe will display the row names if it has them.

The second case is when the dataframe has been converted to a tibble. The row names have been discarded by default. The third is a tibble with the row names intentionally kept. It has a * to show that the row names exist, but they are not displayed.

[acullum]

Ah, thank you. I assumed that rownames = NA set the row names to missing/not available. I have to say it seems counterintuitive that NA means keep the names, but I see (having read the help) that NULL would be how you'd explicitly indicate row names should be dropped.