how to use facet_wrap to ggplot multiple location point in R? - r

Question

I am trying to plot multiple location data using facet_wrap functionality of ggplot. I am having trouble in creating the legends (95% confidence interval is completely missed). Below is my code and I would appreciate any suggestion.
library(ggplot2)
library(lubridate)
set.seed(123)
DF1 <- data.frame(Date = seq(as.Date("2001-01-01"), to = as.Date("2005-12-31"), by = "1 month"),
Ob = runif(60,1,5), L95 =runif(60, 0,4), U95 = runif(60,2,7), Sim = runif(60,1,5),
Loc = rep("Upstream", 60))
DF2 <- data.frame(Date = seq(as.Date("2001-01-01"), to = as.Date("2005-12-31"), by = "1 month"),
Ob = runif(60,1,5), L95 =runif(60, 0,4), U95 = runif(60,2,7), Sim = runif(60,1,5),
Loc = rep("Downstream", 60))
DF <- dplyr::bind_rows(DF1,DF2)
DF$Loc <- factor(DF$Loc, levels = c("Upstream","Downstream"))
ggplot(DF, aes(x = Date))+
geom_ribbon(aes(ymin = L95, ymax = U95), fill = "grey30", alpha = 0.4)+
geom_line(aes(y = Ob, color = "blue"), size = 1 )+
geom_line(aes(y = Sim, color = "black"), size = 1, linetype = "dashed")+
geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30)+
facet_wrap(~ Loc, ncol = 1, scales = "free_y")+
theme_bw()+
scale_color_identity(guide = "legend", breaks = c("grey30", "blue", "black"),
labels = c("95% confidence bound", "Observation","Simulation"))

Answer 1

Your fill is outside the aes function, so it cannot appear in the legend.
ggplot(DF, aes(x = Date))+
geom_ribbon(aes(ymin = L95, ymax = U95, color = "grey30"), fill = "grey30", alpha = 0.4)+
geom_line(aes(y = Ob, color = "blue"), size = 1 )+
geom_line(aes(y = Sim, color = "black"), size = 1, linetype = "dashed")+
geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30)+
facet_wrap(~ Loc, ncol = 1, scales = "free_y")+
theme_bw()+
scale_color_identity(guide = "legend", breaks = c("grey30", "blue", "black"),
labels = c("95% confidence bound", "Observation","Simulation"))
ggplot(DF, aes(x = Date))+
geom_ribbon(aes(ymin = L95, ymax = U95, fill = "grey30"), alpha = 0.4)+
geom_line(aes(y = Ob, color = "blue"), size = 1 )+
geom_line(aes(y = Sim, color = "black"), size = 1, linetype = "dashed")+
geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30)+
facet_wrap(~ Loc, ncol = 1, scales = "free_y")+
theme_bw()+
scale_color_identity(guide = "legend", breaks = c( "blue", "black"),
labels = c( "Observation","Simulation"),
name = 'Legend')+
scale_fill_identity(guide = "legend", labels = c("95% confidence bound"),
name=NULL)+
theme(legend.spacing.y = unit(-0.2, "cm"))+
theme(legend.title = element_text(margin=margin(b = 0.4, unit='cm')))

Answer 2

Here is how I would do this.
First, you are using fill for the ribbon, not color. Second, you need to actually map fill in aes, not just set it outside the aes. Then I would give the names you'd like in the aes calls, and use scale_*_manual to set the values you'd like:
ggplot(DF, aes(x = Date))+
geom_ribbon(aes(ymin = L95, ymax = U95, fill = "95% confidence bound"), alpha = 0.4)+
geom_line(aes(y = Ob, color = "Observation"), size = 1 )+
geom_line(aes(y = Sim, color = "Simulation"), size = 1, linetype = "dashed")+
geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30)+
facet_wrap(~ Loc, ncol = 1, scales = "free_y")+
theme_bw()+
scale_color_manual(values = c('blue', 'black'), name = NULL) +
scale_fill_manual(values = 'grey30', name = NULL)
There are a number of valid ways to approach this, but this is how many people do it.