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Let’s add a fit line to a scatterplot!

### Fit Line in Base Graphics

Here’s how to do it in base graphics:

ols <- lm(Temp ~ Solar.R,
data = airquality)

summary(ols)

plot(Temp ~ Solar.R,
data = airquality)
abline(ols)


 Fit line in base graphics in R

### Fit Line in ggplot

And here's how to do it in ggplot:

library(ggplot2)
ggplot(data = airquality,
aes(Solar.R, Temp)) +
geom_point(pch = 19) +
geom_abline(intercept = ols$coefficients[1], slope = ols$coefficients[2])


You can access the info from your regression results through ols\$coefficients.
 Fit line in ggplot in R

### Fit Line in Lattice

In lattice, it's even easier. You don't even need to run a regression; you can just add to the type option.

library(lattice)

xyplot(Temp ~ Solar.R,
data = airquality,
type = c("p", "r"))


 Fit Line in Lattice in R
The code is available in a gist.