在ggplot2上制作传奇

Question

如何在此代码中添加图例？

谢谢！

ggplot()+ 
  geom_point(data=avg_harv_df, aes(x=samp_per, y=ndvi), size=3, color='red') + 
  geom_point(data=avg_sjer_df, aes(x=samp_per, y=ndvi), size=3, color='blue') +
  ylab("NDVI")+
  xlab("Sampling period")

Answer 1

选项1：

ggplot()+ 
  geom_point(data=avg_harv_df, aes(x=samp_per, y=ndvi, col = "a"), size=3) + 
  geom_point(data=avg_sjer_df, aes(x=samp_per, y=ndvi, col = "b"), size=3) +
  ylab("NDVI")+
  xlab("Sampling period")

选项2：

combined <- dplyr::bind_rows(avg_harv_df, avg_sjer_df, .id = 'col')
ggplot(combined, aes(x=samp_per, y=ndvi, col = col))+ 
  geom_point(size=3) + 
  ylab("NDVI")+
  xlab("Sampling period")

我几乎总是喜欢选项2。