I have seen the answer for this question but I have K groups, each of them with n[k] elements, and I want to draw for example floor(n[k] * p) samples from each of these groups.
I was thinking something like this:
df %>%
group_by(my_group) %>%
mutate(
n_samples = floor(n() / 2)
) %>%
sample_n(n_samples)
But that doesn't work because the argument for sample_n should be the same for every group.
I prefer solutions using dplyr or at least following the tidyverse convention.