I am new to R language, making my first steps. What I have done wrong here ?

[MuhammadAbdulMaksoud]

[EconProf]

After you removed the extra ) at the end of the last line the code ran correctly and filtered_toothgrowth should be under the Environment tab in the upper-right pane.

The group="drop" creates a new variable named group with values of drop. If you want to specify a grouping structure for the result, use .groups = . For this example, it is not needed.

library(tidyverse)

ToothGrowth %>%
  filter(dose == 0.5) %>%
  group_by(supp) %>%
  summarise(mean_len = mean(len, na.rm = TRUE), group = "drop")
#> # A tibble: 2 × 3
#>   supp  mean_len group
#>   <fct>    <dbl> <chr>
#> 1 OJ       13.2  drop 
#> 2 VC        7.98 drop

ToothGrowth %>%
  filter(dose == 0.5) %>%
  group_by(supp) %>%
  summarise(mean_len = mean(len, na.rm = TRUE), .groups = "drop")
#> # A tibble: 2 × 2
#>   supp  mean_len
#>   <fct>    <dbl>
#> 1 OJ       13.2 
#> 2 VC        7.98

ToothGrowth %>%
  filter(dose == 0.5) %>%
  group_by(supp) %>%
  summarise(mean_len = mean(len, na.rm = TRUE))
#> # A tibble: 2 × 2
#>   supp  mean_len
#>   <fct>    <dbl>
#> 1 OJ       13.2 
#> 2 VC        7.98

^{Created on 2023-02-25 with reprex v2.0.2}