R ggplot2 to plot bars for group mean

Question

I'm using the dataset from the package "gapminder" which has a variable "continent" and a variable "lifeExp" (life expectancy). I used -mutate- function to calculate the mean and sd of lifeExp for each continent and add this variable into the dataset (so each observation will have a mean of lifeExp), it will be like this: 1 When I want to use -ggplot2- package to plot bars of means of "lifeExp" (variable "mean") by "continent", it seems that R will sum up the value of "mean" like this: 2

My code is:

gap2007 %>%
  ggplot(., aes(x=continent, y=mean, fill=continent))+
  geom_bar(stat='identity')+
  geom_errorbar(aes(ymin=mean-sd, ymax=mean+sd))+
  xlab("Continent") + ylab("Mean life expectancy") +
  labs(title="Barplot of Average Life Expectancy with Standard Deviations")

How to plot in group level of mean not summing up the mean? Thank you!

Answer 1

It appears that you calculated the means of lifeExp by country , then you plotted those values by continent . The easiest solution is to get the data right before ggplot , by calculating mean and sd values by continent :

library(tidyverse)
library(gapminder)

df<-gapminder %>% 
  group_by(continent) %>% 
  summarize(
    mean = mean(lifeExp), 
    median = median(lifeExp), 
    sd = sd(lifeExp)
  ) 

df %>%
  ggplot(., aes(x=continent, y=mean, fill=continent))+
  geom_bar(stat = "identity")+
  geom_errorbar(aes(ymin=mean-sd, ymax=mean+sd))+
  xlab("Continent") + ylab("Mean life expectancy") +
  labs(title="Barplot of Average Life Expectancy with Standard Deviations")

^{Created on 2020-01-16 by the reprex package (v0.3.0)}