Feature request: Add show_regressionline (or similar)

[roaldarbol]

In some fields, regression lines on point plots are only added when a regression coefficient is significant. In those cases it would be great to have a way to still plot the residuals (with show_residuals=TRUE), turn off the confidence interval (show_ci=FALSE), and also disable plotting the regression line itself (so show_regressionline/show_line or something along those lines).

I've tried to get to the residuals myself (also mentioned in #627) which would allow me to make a plot myself, but have not been successful until now.

---

Have found a temporary solution, which is to set the layer to NULL:

library(ggeffects)
data("mtcars")
lm_c <- lm(hp ~ wt + vs, data = mtcars)
c_pred <- predict_response(lm_c, "wt")
p_c <- plot(c_pred, show_residuals = TRUE, show_ci = FALSE)
#> Data points may overlap. Use the `jitter` argument to add some amount of
#>   random variation to the location of data points and avoid overplotting.
p_c$layers[[2]] <- NULL
p_c

^{Created on 2025-01-18 with reprex v2.1.1}