Percentage in a original ggplot count barplot

I have this code:

 tbl <- with(mydata, table(Species, Depth))
library(ggplot2)
ggplot(as.data.frame(tbl), aes(factor(Depth), Freq, fill = Species)) +     
  geom_col(position = 'dodge')

and this dataframe

    Site Depth Substrate PoePres HaliPres Species
1      2   0.5      Sand       0        1  DMonte
2      2   0.5      Sand       0        1  DMonte
3      2   0.5      Sand       0        1  DMonte
4      2   0.5      Sand       0        1  DMonte
5      2   0.5      Sand       0        1  DMonte
6      2   0.5      Sand       0        1  DSandi
7      2   0.5      Sand       0        1  DSandi
8      2   0.5      Sand       0        1  DSandi
9      7   0.6      Sand       0        1  DMonte
10     7   0.6      Sand       0        1  DMonte
11     7   0.6      Sand       0        1  DMonte

That I took from this other question: Bar plot for count data by group in R

I would like to know how I could plot percentage per group (‘Depth’ in this case) rather than counts.

Thanks

>Solution :

Another option by first calculate the percentage value per group_by and use percent from scales to create percentage axis like this:

library(ggplot2)
library(dplyr)
library(scales)

mydata %>% 
  count(Species, Depth) %>% 
  group_by(Depth) %>% 
  mutate(pct = n / sum(n)) %>%   
  ggplot(aes(x = factor(Depth), y = pct, fill=factor(Species))) + 
  geom_col(position="dodge") +
  scale_y_continuous(labels = percent) +
  labs(x = 'Depth', fill = 'Species')

^{Created on 2022-11-14 with reprex v2.0.2}