I tried to add custom legend into my R plot that uses same x value but two different y values. I used the approach from the following post but it does not work:
Custom legend for multiple layer ggplot
ggplot(combo_plot, aes(x))+
geom_point(aes(y=y1),size=2,color="black")+
geom_point(aes(y=y2),size=2,color="red")+
coord_cartesian(xlim = c(0,1.25),ylim=c(200,450)) +
scale_x_continuous(breaks = seq(0,1.25,0.25), minor_breaks = seq(0,1.5,0.25),expand = c(0, 0)) +
scale_y_continuous(breaks = seq(200,450,25), minor_breaks = seq(200,450,25),expand = c(0, 0)) +
scale_colour_manual(name = 'the colour',
values =c('black'='black','red'='red'), labels = c('c2','c1'))+
theme(plot.title = element_text(family = "GE Inspira", color="#666666", face="bold", size=16, hjust=0.5))+
theme(axis.title = element_text(family = "GE Inspira", color="#666666", face="bold", size=12, hjust=0.5))
Any idea why it does not work in this case?