Data signatures on a guitogram - r

Question

Good afternoon, dear pros.
I ask you to suggest answers to some questions that I could not understand. There is the following set of data:
df<-data.frame(num = c(1:20),
gender=unlist(strsplit("MFFMMMFMFMMMMMFFFMFM","")),
age= sample(1:100, 20, replace=T),
entrance=sample(1:4, 20, replace=T))
The data is sorted and grouped.
df <- group_by(df, df$entrance, df$gender)
Actually, according to the data, a graph is built
ggplot(df, aes(x= df$entrance)) +
geom_bar(aes(fill=df$gender), position = "dodge")+
scale_fill_discrete(name = "Title", labels = c("F", "M"))+
xlab("Distribution of residents by entrances, taking into account gender")+
ylab("Number of residents")
Actually, here's the result:
What I do not like?
I would like that if there is no data in the category, then the column is not drawn, but 0 is indicated.
Also I would like to have data labels like in the picture below.
Well, I would also like options for placing these values:
bottom (as drawn);
in the center of the strip;
on top of the strip.

Answer 1

Try this. You can get something similar to what you expect using facets and changing some aesthetic elements:
library(ggplot2)
library(dplyr)
#Plot
df %>% group_by(entrance,gender) %>%
summarise(N=n()) %>%
mutate(gender=factor(gender,levels = c('F','M'))) %>%
complete(gender,fill = list(M=0,F=0)) %>%
replace(is.na(.),0) %>%
ggplot(aes(x= factor(gender),y=N,fill=gender)) +
geom_bar(stat='identity', position = position_dodge2(0.9))+
geom_text(aes(label=N,y=0),vjust=-0.5,position = position_dodge2(0.9))+
scale_fill_discrete(name = "Title", labels = c("F", "M"))+
facet_wrap(.~entrance,nrow = 1,strip.position = 'bottom')+
xlab("Distribution of residents by entrances, taking into account gender")+
ylab("Number of residents")+
theme(strip.placement = 'outside',
strip.background = element_blank(),
axis.text.x = element_blank(),
axis.ticks.x = element_blank())
Output: