将闪亮的传单世界地图缩放至全宽

Question

有谁知道如何设置 Shiny Leaflet 地图的默认渲染缩放，以便完整的世界地图缩放以适​​合窗口宽度（即 -180° 到 180° 适合窗口）？我只能将缩放设置为整数，2太小和3太大。可重现的例子：

require(shiny)
require(leaflet)
require(magrittr)

d = data.frame(country = c('China', 'Brazil', 'Canada'), lon = c(105, -52, -95), lat = c(35, -10, 60))

server <- function(input, output, session) {

  output$mymap <- renderLeaflet({
    leaflet(d) %>% 
      addCircleMarkers(layerId = ~country, lng = ~lon, lat = ~lat, label = ~ country, radius=30) %>% 
      addProviderTiles(providers$Stamen.TonerLite, options = providerTileOptions(noWrap = TRUE,  minZoom=1, maxZoom=18)
      )
  })
}

ui <- fluidPage( 
  tags$head(tags$style(HTML("#mymap { position: fixed; left: 0; top: 0; width: 100vw; height: 100vh !important; }"))
  ),
  leafletOutput("mymap") 
)

shinyApp(ui, server)