Plotly in R - Diagonal AB line

Question

I require a diagonal line through the origin of this plot

Something similar to ggplot2's geom_abline(intercept = 0 , slope = 1) But for plotly in R

library(plotly)

fig <- plot_ly(data = iris, x = ~Sepal.Length, y = ~Petal.Length)
fig

Answer 1

A line shape could be used to achive this:

library(plotly)

fig <- plot_ly(data = iris, x = ~Sepal.Length, y = ~Petal.Length)
fig %>%
  layout(shapes = list(list(
    type = "line", 
    x0 = 0, 
    x1 = ~max(Sepal.Length, Petal.Length), 
    xref = "x",
    y0 = 0, 
    y1 = ~max(Sepal.Length, Petal.Length),
    yref = "y",
    line = list(color = "black")
  )))

Also see this related answer.

Btw. via xref = "paper" we don't need to specify start and end points for the line, however the line is no longer aligned with the axes.

Answer 2

Kindly let me know if this is what you were anticipating.

fit <- lm(Petal.Length ~ Sepal.Length, data = iris)

iris %>% 
  plot_ly(x = ~Sepal.Length) %>% 
  add_markers(y = ~Petal.Length) %>% 
  add_lines(x = ~Sepal.Length, y = fitted(fit))