add standard deviation in ggplot?

[Lucas11]

Hi, I have this code and I would like to add a line with the standar deviation to my ggplot

example <- data.frame (var1 = c ("ESP", "AUT", "POR", "GRE", "ITA", "USA", "FRA", "GER", "DEN", "BRA", "AUS", "NZ", "CHI","JAP"),                     					  					         	          
                       var2 = c(91, 29, 83, 49, 58, 68, 77, 88, 90, 34, 10, 91, 50, 46),                        			        		          
                       var3 = c (1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0),                       			        		          
                       var4 = c("EUR","EUR","EUR","EUR","EUR","AME", "EUR", "EUR", "EUR","AME", "OCE","OCE", "ASI", "ASI"))

example %>% 
  group_by(var4) %>% 
  summarise(mean_var2 = mean(var2),
            sd_var2 = sd(var2)) %>% 
  ggplot(aes(x = var4, y = mean_var2))+
  geom_point() 

Now I am getting this

I would like to add sd_var2 to the points in each continent. It would be great if I could keep using the pipes and the group_by and summarize code.

[yifanliu]

Do you mean add SD as an error bar? like

example %>% 
  group_by(var4) %>% 
  summarise(mean_var2 = mean(var2),
            sd_var2 = sd(var2)) %>% 
  ggplot(aes(x = var4, y = mean_var2))+
  geom_point() +
  geom_pointrange(aes(ymin = mean_var2 - sd_var2, 
                      ymax = mean_var2 + sd_var2))