Leaflet R图例未显示较大的数据集

Question

我有一个如下所示的数据框：

head(mydf)
  id      lat       lon type
1  1 40.43859 -79.96828    2
2  2 40.58657 -79.76769    1
3  3 40.53450 -79.21241    2
4  4 40.41032 -79.86355    2
5  5 40.44095 -80.06801    2
6  6 40.35060 -79.85733    2

我正在使用传单进行这样的绘制，除了显示的图例外，它的工作正常：

library(leaflet)
factpal <- colorFactor(c('#FF7F0E', '#1F77B4', '#2CA02C', '#E41A1C'), mydf$type)
mydf %>%  leaflet() %>%
    setView(-95, 35, 4) %>% addProviderTiles("Stamen.TonerLite",
                     options = providerTileOptions(noWrap = TRUE)) %>%
    addCircles(radius = 10, color = ~factpal(type)) %>%
    addLegend(position = 'bottomright', pal = factpal, values = ~type, opacity = 1)

但是，图例不显示我的30K +行数据集。奇怪的是，当我对整个数据集采样较小的数据帧时，图例显示完美。我的代码或addLegend有什么问题？

这有效：

mydfSub <- mydf[sample(1:nrow(mydf), 1000), ]
mydfSub %>%  leaflet() %>%
    setView(-95, 35, 4) %>% addProviderTiles("Stamen.TonerLite",
                     options = providerTileOptions(noWrap = TRUE)) %>%
    addCircles(radius = 10, color = ~factpal(type)) %>%
    addLegend(position = 'bottomright', pal = factpal, values = ~type, opacity = 1)