library(plotly)

df <- data.frame(x = runif(200), y = runif(200), z = runif(200), j = runif(200), k = rep(0.7, 200), i = rnorm(200,0.6,0.05))

create_buttons <- function(df, y_axis_var_names) {
  lapply(
    y_axis_var_names,
    FUN = function(var_name, df) {
      button <- list(
        method = 'restyle',
        args = list('y', list(df[, var_name])),
        label = sprintf('Show %s', var_name)
      )
    },
    df
  )
  
}

y_axis_var_names <- c('y', 'z', 'j', 'k', 'i')

p <- plot_ly(df, x = ~x, y = ~y, mode = "markers", name = "A", visible = T) %>%
     layout(
         title = "Drop down menus - Styling",
         xaxis = list(domain = c(0.1, 1)),
         yaxis = list(title = "y"),
         updatemenus = list(
             list(
                 y = 0.7,
                 buttons = create_buttons(df, y_axis_var_names)
             )
         ))
p