How to add percentage above the ggplot graph bars?

Question

How can I add the percentage above the bars from a data.frame?

How could I use two decimal places after the comma.

I tried to apply ggplot, but I couldn't get it wrong:

a <- c("até 50","50-150","150-500","500-2000")
b <- c(107,38,14,3)
pcent <- c(66.049383, 23.456790, 8.641975, 1.851852)

df <- data.frame(a,b,pcent)

ggplot(df, aes (x=reorder(a, -b), y=b, label=pcent)) +
  geom_col(fill="#70A2E7") +
  labs(x = "Faixa de desmatamento (ha)", y="Quantidade de polígonos de desmatamento", title = "Distribuição dos polígonos de desmatamento") +
  geom_text(aes(y = pcent, label = scales::percent(pcent)), vjust = -0.2)+
   scale_y_continuous(labels = scales::percent)

Answer 1

Your y-axis is raw count and you want to plot percentage on top of bars which can be bit misleading. Anyway, you can do :

library(ggplot2)
ggplot(df, aes (x=reorder(a, -b), y=b, label=pcent)) +
  geom_col(fill="#70A2E7") +
  labs(x = "Faixa de desmatamento (ha)", 
       y="Quantidade de polígonos de desmatamento", 
       title = "Distribuição dos polígonos de desmatamento") +
  geom_text(aes(label = paste0(round(pcent,2), '%')), vjust = -0.5)

Or probably better to show percentages on y-axis.

ggplot(df, aes (x=reorder(a, -b), y=pcent, label=pcent)) +
  geom_col(fill="#70A2E7") +
  labs(x = "Faixa de desmatamento (ha)", 
       y="Quantidade de polígonos de desmatamento", 
       title = "Distribuição dos polígonos de desmatamento") +
  geom_text(aes(label = paste0(round(pcent,2), '%')), vjust = -0.5) + 
  scale_y_continuous(labels = function(x) paste0(x, '%'))