How do I use gganimate on a bar plot so each bar that appears doesn't disappear until the animation ends?

Question

Each bar appears and then disappears before the next one does. I'm copying the code I'm using here:

library(ggplot2)
library(gganimate)

med_age <- c(18,31,31,33,35,42)
continent <- c("Africa","South America","Asia","North & Central America","Oceania","Europe")
cont_colors <- c("tan2","yellowgreen","tomato1","lightpink2","seagreen2","steelblue2")
#create data frame
age_continent <- data.frame(continent,med_age)

Plot:

age_animate <- ggplot(data=age_continent,aes(x=continent,y=med_age))+
geom_bar(stat = "identity",fill=cont_colors)+
geom_text(aes(label=med_age), vjust=1.6, color="black", size=5)+
theme_minimal()+
theme(axis.text.y=element_blank(),panel.grid=element_blank(),axis.text=element_text(size=10))+
xlab("")+
ylab("")+
ggtitle("Median Age by Continent", subtitle = "Source: www.visualcapitalist.com")+
transition_states(continent)

animate(age_animate)

Answer 1

A little modified primary answer from stefan!!

library(ggplot2)
library(gganimate)

med_age <- c(18,31,31,33,35,42)
continent <- c("Africa","South America","Asia","North & Central America","Oceania","Europe")
cont_colors <- c("tan2","yellowgreen","tomato1","lightpink2","seagreen2","steelblue2")
#create data frame
age_continent <- data.frame(continent,med_age)

  
  age_animate <- ggplot(data=age_continent,aes(x=continent,y=med_age))+
  geom_bar(stat = "identity",fill=cont_colors)+
  geom_text(aes(label=med_age), vjust=1.6, color="black", size=5)+
  theme_minimal()+
  theme(axis.text.y=element_blank(),panel.grid=element_blank(),axis.text=element_text(size=10))+
  xlab("")+
  ylab("")+
  ggtitle("Median Age by Continent", subtitle = "Source: www.visualcapitalist.com")+
  transition_states(continent, wrap = FALSE) + 
  shadow_mark() +
  enter_grow() +
  enter_fade()

anim <- animate(age_animate)
anim_save("age_animate.gif", anim)

Answer 2

This could be achieved via shadow_mark() which

... lets you show the raw data behind the current frame. Both past and/or future raw data can be shown and styled as you want.

See here.

library(ggplot2)
library(gganimate)

med_age <- c(18,31,31,33,35,42)
continent <- c("Africa","South America","Asia","North & Central America","Oceania","Europe")
cont_colors <- c("tan2","yellowgreen","tomato1","lightpink2","seagreen2","steelblue2")

age_continent <- data.frame(continent,med_age)
  
age_animate <- ggplot(data=age_continent,aes(x=continent,y=med_age))+
  geom_bar(stat = "identity",fill=cont_colors)+
  geom_text(aes(label=med_age), vjust=1.6, color="black", size=5)+
  theme_minimal()+
  theme(axis.text.y=element_blank(),panel.grid=element_blank(),axis.text=element_text(size=10))+
  xlab("")+
  ylab("")+
  ggtitle("Median Age by Continent", subtitle = "Source: www.visualcapitalist.com")+
  transition_states(continent) +
  shadow_mark()

animate(age_animate)