我正在尝试在ggplot2上添加图例。

当我使用以下代码时，我得到以下图。

ggplot() + 
  geom_bar(data = profitCountries,aes(y = (revenue),x = residence),stat="identity",fill="darkgreen",color = "black") +

  geom_bar(data = profitCountries,aes(y = -(total_spend),fill="red",color = "black") +

  geom_line(data = profitCountries,aes(y = total_profit,x = residence,group = 1),size = 1.5,color = "blue"  ) + 

  scale_y_continuous(breaks = seq(-500000,500000,100000),limits=c(-500000,500000) ) +
  xlab('Countries') + ggtitle('Campaign spending and revenue by countries') + 
  ylab('Campaign spending                                     Revenue')  + theme_grey()

根据其他帖子的建议，我在color内添加了aes()。当我尝试使用以下代码进行操作时，得到以下图表。

ggplot() + 
  geom_bar(data = profitCountries,fill="darkgreen"),fill="red"),group = 1,color = "blue"),size = 2 ) + 

  scale_y_continuous(breaks = seq(-500000,500000) ) +
  xlab('Countries') + ggtitle('Campaign spending and revenue by countries') + 
  ylab('Campaign spending                                     Revenue')  + theme_grey()

在第二个图中，颜色改变，并创建了两个图例。反正有解决办法吗？