layer_abline() for ggvis

layer_abline.R

abline_data <- function (domain, intercept, slope) {
  data.frame(x = domain, y = domain * slope + intercept)
}

untick <- function (x) {
  stopifnot(all(sapply(x, is.name)))
  str_replace_all(as.character(x), "`", "")
}

layer_abline <- function (.vis, domain, intercept = 0, slope = 1, dash = 6, ...) {
  df <- abline_data(domain, intercept, slope)
  names(df) <- with(.vis$cur_props, untick(c(x.update$value, y.update$value)))
  layer_paths(.vis, data = df, ..., strokeDash := dash)
}