两个变量并排条形图ggplot

Question

Image of sample data

试图制作一个并排的条形图，但条形图似乎在彼此之后，但不能让它们并排：看图像

afg <- read.table(header=TRUE,
text="FG  biomass stdev   Year
1   287.6   237.5   2015
1   254.2   220.6   2016
2   309.9   126.3   2015
2   307.6   139.5   2016
3   339.6   175.5   2015
3   349.3   160.6   2016")

library(ggplot2)
ggplot(afg,aes(afg$FG,afg$biomass,fill=afg$Year)) +
geom_bar(stat="identity",position=position_dodge(0.9),color="black")

library(reshape2)
afg.long <- melt(afg$Year,id="year")
ggplot(afg.long,aes(afg$FG,afg$biomass,fill=afg$Year)) +
geom_bar(stat="identity",position = "dodge")

Answer 1

为了将其视为分类变量，您的列Year需要转换为factor类型。另请注意，$函数中不应使用aes()的变量选择。

library(ggplot2)

p <- ggplot(afg, aes(x=FG, y=biomass, fill=factor(Year))) +
     geom_bar(stat="identity", position="dodge")

ggsave("dodged_barplot.png", plot=p, height=4, width=6, dpi=150)


# Note that 'Year' is type integer.

str(afg)
# 'data.frame': 6 obs. of  4 variables:
#  $ FG     : int  1 1 2 2 3 3
#  $ biomass: num  288 254 310 308 340 ...
#  $ stdev  : num  238 221 126 140 176 ...
#  $ Year   : int  2015 2016 2015 2016 2015 2016