How can I display correctely color referencing in legend?-CodePudding

I am reopening the discussion I had here: Problem displaying correct data in legend

I would like to know if there is an easy way to display legend color references when 2 parameters have the same color curves or points. Here is the script showing that the plot's legend displays only one of the 2 parameters in red:

library("tidyverse")
library("lubridate")
library("ggplot2")

Time <- c("09-01-2023 12:07:09","09-01-2023 12:17:09","09-01-2023 12:27:09","09-01-2023 12:37:09")
Width <- c(3,4,5,6)
Length <- c(30,40,50,60)
Weight <- c(300,400,500,600)
Angle <- c(3000,4000,5000,6000)

DF <- data.frame(Time,Width,Length,Weight,Angle)
DF<- DF %>% mutate(Time=dmy_hms(Time))
DF_Tidy<-gather(DF,key=Parameters,value=Values,-Time)   
Colors<-c("red","red","red","red","blue","blue","blue","blue",
          "red","red","red","red","green","green","green","green")
Units <-c("mm","mm","mm","mm","mm","mm","mm","mm","kg","kg","kg","kg","Deg","Deg","Deg","Deg")
DF_Tidy<-data.frame(DF_Tidy,Units,Colors)
Graph_DF<-DF_Tidy %>%
ggplot(aes(x=Time, y=Values,color=Colors))  
geom_point()  
scale_color_identity(
guide = "legend",
labels = setNames(DF_Tidy$Parameters, DF_Tidy$Colors)) 
theme(axis.text.x = element_text(size = 10),axis.text.y = element_text(size = 10),
legend.text=element_text(size=8),legend.key.size = unit(0.5,"line"),legend.position = "bottom") 
facet_wrap(facets = (~ Units),scales="free_y",nrow=4)
plot(Graph_DF)  `

I have attached the plot legend result. If I replace one the 2 sets of 4 red colors by a set of 4 brown colors, I do get 4 colors (red, blue, brown, green) in my legend (because there are no 2 parameters with the same color (red))

enter image description here

In other words, I would like the legend to appear as below:

blue point: Length red point: Width red point: Weight green point: Deg

Is there a way to do this (another way than the one provided in my last post)? Thank you for your help. User

CodePudding user response：

Add:

guides(color = guide_legend(label.position = "left"))

to the call to ggplot.

^{Created on 2023-01-13 with reprex v2.0.2}

CodePudding user response：

Maybe you want to use interaction to combine the color and shape to have 2 labels with red colors like this:

library(tidyverse)
library("lubridate")
library("ggplot2")

Graph_DF<-DF_Tidy %>%
ggplot(aes(x=Time, y=Values,color=interaction(Colors, Parameters), shape = interaction(Colors, Parameters)))  
  geom_point()  
     scale_colour_manual(name = "legend",
                   values = c("blue", "green", "red", "red"),
                   labels = c("Length", "Deg", "Width", "Weight")) 
     scale_shape_manual(name = 'legend',
                   values = c(16, 16, 16, 17),
                   labels = c("Length", "Deg", "Width", "Weight")) 
     theme(axis.text.x = element_text(size = 10),axis.text.y = element_text(size = 10),
                       legend.text=element_text(size=8),legend.key.size = unit(0.5,"line"),legend.position = "bottom") 
                 facet_wrap(facets = (~ Units),scales="free_y",nrow=4)
plot(Graph_DF)

^{Created on 2023-01-13 with reprex v2.0.2}