ggplot 中的条形图和 geom_line

Question

我正在尝试在条形图上绘制 geom_line，我的条形是按年份填充的。我的代码是：

library(ggplot2)
library(plyr)
library(reshape)

DF <- data.frame(DECL.INDICATORS=c("Finland", "Finland", "Germany" ,"Germany","Italy","Italy"),
                 Year=c(2009,2010,2009,2010,2009,2010),
                 EXPVAL=c(2136410,1462620,371845300,402397520,357341970,357341970),
                 IMPVAL=c(-33668520,-37837140,-283300110,-306157870,-103628920,-105191850))


net <- ddply(DF, .(Year,DECL.INDICATORS), summarise, 
                net = sum(EXPVAL + IMPVAL))

DF.m <- melt(DF, id.vars = c("Year", "DECL.INDICATORS"))

ggplot(DF.m,aes(x=DECL.INDICATORS,y=value, fill=factor(Year)))+
  geom_bar(stat="identity",position="dodge",colour="darkgreen")

last_plot() + geom_line(data = net, aes(DECL.INDICATORS, net,group = 1), size = 1) + geom_hline(yintercept = 0,colour = "grey90")

我要解决的问题是为每个国家/地区芬兰、德国、意大利画一条三线（net 的净出口）。

在我的最后一行代码中，我只得到了三个与线相连的点

Answer 1

您应该改用构面。这样一来，很明显您只是在一个国家内部进行比较，而不是在国家之间进行比较。

ggplot(DF.m, aes(x = factor(Year), y = value, fill = factor(Year))) +
  geom_bar(stat = "identity", position = "dodge", colour="darkgreen") + 
  facet_grid(~DECL.INDICATORS) + 
  geom_line(data = net, aes(y = net, group = 1))

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