我用ggplot2画三条固定斜率和截距的直线，如下
library(ggplot2)
library(grid)

ggplot() +
  geom_abline(aes(color = "Num = 12", linetype = "Num = 12"), intercept = -0.0005669, slope = -0.1099574) +
  geom_abline(aes(color = "Num = 1", linetype = "Num = 1"), intercept = -0.0004009, slope = -0.0515904) +
  geom_abline(aes(color = "Num = 0", linetype = "Num = 0"), intercept = -0.0003858, slope = -0.0462843) +
  xlim(0.015, maxx) + ylim(-0.015, 0) +
  ylab("UE") + xlab("SS") +
  ggtitle("XXX") +
  theme(plot.title=element_text(face="bold", size=12, vjust=2),  
        axis.title.x=element_text(vjust=-1, size=12),
        axis.title.y=element_text(hjust=1, size=12, angle = 0),
        plot.margin=unit(c(1,1,1,1), "cm"))+
  scale_color_manual(name = "Number", values=c("Num = 12"="red", "Num = 1"="blue", "Num = 0"="black")) +
  scale_linetype_manual(name = "Number", values=c("Num = 12"=2, "Num = 1"=1, "Num = 0"=9))


查了一下ggplot2的资料，貌似用 scale_linetype_manual 和  scale_color_manual可以画出legend，但是我这个代码怎么都不出legend，请各位帮忙看看哪出问题了。多谢多谢！