Add line in GGplot2

[tnf1508]

I want to keep my site names as different colors and keep my legend. I want to add only 1 line though, instead of each Site having a line of best fit. How do I do this?

[pcall]

Hi there,

A reprex or even just a copy/paste of your code would be easier to work off of, for future reference.

In any case, I think the code below is roughly what you're looking for with particular regards to the inherit.aes argument in geom_smooth in addition to the other arguments you might specify about the method, standard error, etc.

ggplot(your_data, aes(var1, var2, var3 ...)) +
geom_point() +
geom_smooth(data=your_data, aes(var1, var2), inherit.aes=F, ...)

The details: geom_*() functions automatically inherit aesthetics defined in ggplot(data, aes()). This is generally the preferred approach to using ggplot(), but you can write out aesthetics individually in each geom_*() function or use inherit.aes=F to circumvent this standard approach.

[nirgrahamuk]

I think pcall gave you excellent advice.
Here is an example in action

library(tidyverse)

RShiner <- iris %>% 
  rename(Body.Length=Petal.Length,
         Eye.Size = Sepal.Width,
         Site.Name = Species)


Plot.BL.EyeSize.RShiner<-ggplot(data=RShiner,aes(x=Body.Length, y=Eye.Size, color=Site.Name))+
  geom_point()+
  geom_smooth(method=lm, se=FALSE, fullrange=FALSE,
              aes(x=Body.Length, y=Eye.Size),
              inherit.aes=F)+
  labs(y = "Eye Diameter") +
  labs(x = "Body Length") +
  theme_bw(base_size = 14) +
  theme(panel.grid.major=element_blank(),panel.grid.minor=element_blank(),panel.border = element_blank()) +
  theme(axis.text.x = element_text(vjust = 0.5))+
  theme(axis.line = element_line(size = 1 ,color = 'black'))+
  theme(axis.title.x = element_text(hjust=0.6, vjust=-0.5, size= 16)) +
  theme(axis.title.y = element_text(hjust=0.5, vjust=0.5, size= 16))

Plot.BL.EyeSize.RShiner

[pcall]

@tnf1508

Plot.BL.EyeSize.RShiner<-ggplot(data=RShiner,aes(x=Body.Length, y=Eye.Size, color=Site.Name))+
geom_point()+
geom_smooth(method=lm, se=FALSE, fullrange=FALSE)

I don't know what your data looks like without a reprex.

Here is a minimal demonstration of the code I mentioned previously using the iris dataset.

ggplot(iris, aes(x=Sepal.Length,y=Petal.Length,color=Species)) +
  geom_smooth(method="lm", se=FALSE, fullrange=FALSE) +
  geom_smooth(data=iris, aes(x=Sepal.Length, y=Petal.Length), 
              inherit.aes = F, method="lm", se=FALSE, fullrange=FALSE)

The first geom_smooth() call creates the lines by species. The second geom_smooth() call, as a result of the inherit.aes=F argument, creates a single line. Note that you have to define data and your aes() arguments again.