Horizontal and Vertical Lines in ggplot2

How to add Horizontal and Vertical Lines in ggplot2 with Plotly.

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Add horizontal line

To do this, use geom_vline():

library(plotly)
library(ggplot2)

p <- ggplot(data=mtcars, aes(x=wt, y=mpg)) + geom_point() +
      geom_vline(xintercept = 3)

ggplotly(p)

Add vertical line

To do this, use geom_hline():

library(plotly)
library(ggplot2)

p <- ggplot(data=mtcars, aes(x=wt, y=mpg)) + 
      geom_point() +
      geom_hline(yintercept=20)

ggplotly(p)

Change line type

library(plotly)
library(ggplot2)

p <- ggplot(data=mtcars, aes(x=wt, y=mpg)) + 
      geom_point() +
      geom_vline(xintercept = 3, linetype="dotted", 
                color = "blue", size=1.5)

ggplotly(p)

library(plotly)
library(ggplot2)

p <- ggplot(data=mtcars, aes(x=wt, y=mpg)) + 
      geom_point() +
      geom_hline(yintercept=20, linetype="dashed", 
              color = "green", size=4)

ggplotly(p)

Add a segment line

If you do not wish to add line that goes across the whole plot, use geom_segment():

library(plotly)
library(ggplot2)

p <- ggplot(data=mtcars, aes(x=wt, y=mpg)) + 
      geom_point() +
      geom_segment(aes(x = 4, y = 15, xend = 4, yend = 27))

ggplotly(p)

Adding regression line

library(plotly)
library(ggplot2)
require(stats)

reg <- lm(mpg ~ wt, data = mtcars)
coeff = coefficients(reg)

eq = paste0("y = ", round(coeff[2],1), "*x + ", round(coeff[1],1))

p <- ggplot(data=mtcars, aes(x=wt, y=mpg)) + geom_point() +
      geom_abline(intercept = 37, slope = -5, color="red", 
                 linetype="dashed", size=1.5)+
      ggtitle(eq)

ggplotly(p)

What About Dash?

Dash for R is an open-source framework for building analytical applications, with no Javascript required, and it is tightly integrated with the Plotly graphing library.

Learn about how to install Dash for R at https://dashr.plot.ly/installation.

Everywhere in this page that you see fig, you can display the same figure in a Dash for R application by passing it to the figure argument of the Graph component from the built-in dashCoreComponents package like this:

library(plotly)

fig <- plot_ly() 
# fig <- fig %>% add_trace( ... )
# fig <- fig %>% layout( ... ) 

library(dash)
library(dashCoreComponents)
library(dashHtmlComponents)

app <- Dash$new()
app$layout(
    htmlDiv(
        list(
            dccGraph(figure=fig) 
        )
     )
)

app$run_server(debug=TRUE, dev_tools_hot_reload=FALSE)