源程序
library(ggplot2)
data2<-read.csv('E:/302.csv',header = F,stringsAsFactors=FALSE, sep=",")
names(data2)<-c('x1','x2','x3','x4','x5','x6','x7','x8','x9','x10')
data2$x10 <- factor(data2$x10)
b = ggplot(data2, aes(x = x4, y = x9, colour=x10)) +   geom_point(size=3)+theme_bw()
b1<-b+xlab(expression(paste("NH4"^"+","-N[mg/（L)]")))+ylab(expression(paste("△N2O[μmol/（L)]")))+geom_abline(intercept = 3.5,slope = 5,size=2)
b1+theme(plot.title = element_text(hjust = 0.5),title=element_text(family="myFont",color="black",size=20) )+scale_shape_discrete(breaks=c('JUN/16','AUG/16','OCT/16','MAY/17','JUL/17'),labels = c('JUN/16','AUG/16','OCT/16','MAY/17','JUL/17'))

这个完全改不了图例顺序，怎么改都不动，求解答