If I have the sample data and plot it using ggplot2 geom_segment :
library(ggplot2)
df1 <- data.frame(p=c(1,2), f=c("A","B"))
df2 <- data.frame(p=c(3,4), f=c("C","D"))
ggplot() +
geom_segment(data=df1, mapping=aes(x=p-0.5, xend=p+0.5, y=1, yend=1, color=f)) +
geom_segment(data=df2, mapping=aes(x=p-0.5, xend=p+0.5, y=1, yend=1, color=f))
the result figure will be :
I can't understand why the two separate geom_segment() layers share the same legend? what is the logic behind this behavior?
How can I manually set the color of line "A" and line "B"? I have tried to change them with the following command:
ggplot() +
geom_segment(data=df1, mapping=aes(x=p-0.5, xend=p+0.5, y=1, yend=1, color=f)) +
scale_color_manual(values=c("A"="red", "B"="blue")) +
geom_segment(data=df2, mapping=aes(x=p-0.5, xend=p+0.5, y=1, yend=1, color=f))
but the error message appears :
Error: Insufficient values in manual scale. 4 needed but only 2 provided.
Thanks you very much