Add abline to legend - r

Question

First, sorry for posting without reproducible data. Hope you guys understand my question. This is my code. At the end of the code, I am trying to add abline. With the code, I am trying to add the name of abline to the legend but it does not work.
ggplot(aes(x = week_id2, y = Index, color = Chain2, linetype = Chain2, group = Chain2),
data = data00 +
geom_point(aes(shape=Chain2), size = 3) +
geom_line() +
scale_linetype_manual(values=c("twodash", "dashed", "dotted", "dotdash", "longdash")) +
scale_shape_manual(values=c(1:5)) +
xlab("Week") +
ylab("Index") +
geom_hline(aes(yintercept=1))
As shown, I just simply add a name of the abline (let's say the name is "add") in the legend. How should I do it with my current code?

Answer 1

You can add either color or linetype to aes then use scale_color_xxx or scale_linetype_xxx to fine tune the legend. Here is an example using economics dataset
library(tidyverse)
df <- economics %>%
select(date, psavert, uempmed) %>%
gather(key = "variable", value = "value", -date)
ggplot(df, aes(x = date, y = value)) +
geom_line(aes(color = variable), size = 1) +
geom_hline(aes(yintercept = 10, color = "My line")) +
scale_color_brewer(palette = "Dark2",
breaks = c("psavert", "uempmed", "My line")) +
theme_minimal()
ggplot(df, aes(x = date, y = value)) +
geom_line(aes(color = variable, linetype = variable), size = 1) +
geom_hline(aes(yintercept = 10, color = "My line", linetype = "My line")) +
scale_color_brewer(palette = "Dark2",
breaks = c("psavert", "uempmed", "My line")) +
scale_linetype_manual(values = c("twodash", "dashed", "dotted"),
breaks = c("psavert", "uempmed", "My line")) +
theme_minimal()
Edit: per OP's request, we separate linetype & color/shape legends
ggplot(df, aes(x = date, y = value)) +
geom_line(aes(color = variable), size = 0.75) +
geom_point(aes(color = variable, shape = variable)) +
geom_hline(aes(yintercept = 10, linetype = "My line")) +
scale_color_brewer(palette = "Dark2",
breaks = c("psavert", "uempmed")) +
scale_linetype_manual("", values = c("twodash"),
breaks = c("My line")) +
scale_shape_manual(values = c(17, 19)) +
# Set legend order
guides(colour = guide_legend(order = 1),
shape = guide_legend(order = 1),
linetype = guide_legend(order = 2)) +
theme_classic() +
# Move legends closer to each other
theme(legend.title = element_blank(),
legend.justification = "center",
legend.spacing = unit(0.1, "cm"),
legend.spacing.y = unit(0.05, "cm"),
legend.margin = margin(0, 0, 0, 0),
legend.box.margin = margin(0, 0, 0, 0))
Created on 2018-05-08 by the reprex package (v0.2.0).