First Plot

library(ggvis)
library(shiny)
mtcars %>% ggvis(x = ~wt, y = ~mpg) %>% layer_points()

Second Plot

span <- input_slider(0.2, 1)

mtcars %>% ggvis(x = ~wt, y = ~mpg) %>%
  layer_points() %>%
  layer_smooths(span = span)
## Warning: Can't output dynamic/interactive ggvis plots in a knitr document.
## Generating a static (non-dynamic, non-interactive) version of the plot.
renderText(span())