r-将传单平铺的可视部分限制为多边形区域

Question

我正在学习如何使用R和传单。我几乎已经完成了使用加利福尼亚州各县绘制地图的工作，但我不喜欢在地图上看到其他州。我想把我的多边形（县）周围的地图涂成白色。我在其他地方看到了类似的问题得到了解决，但我知道的还不够，无法将那里所说的应用到我的代码中。有人能检查一下这个代码并建议我需要添加什么吗？

如果你滚动到这个链接的底部，你会看到我正在尝试做什么。http://rpubs.com/stefanya/127436

我使用的代码是：

#loading shapefile
  counties <- readOGR("./shapefiles", layer="cb_2014_us_county_20m")
#filtering for only california
  counties <- subset(counties, counties@data$STATEFP=="06")
#making a leaflet map of california counties
  leaflet() %>% addTiles() %>% addPolygons(data=counties)
#merging the data into this shapefile
  counties@data = data.frame(counties@data,     sumByCounty[match(counties@data[,"NAME"], sumByCounty[,"NAME"]),])  
#set color palette
  colorRamp <- colorRamp(c("#2c7fb8","#7fcdbb","#edf8b1"), interpolate = "spline")
  palette <- colorNumeric(colorRamp, counties@data$progress)
  leaflet() %>% addProviderTiles("Stamen.TonerLite") %>%
addPolygons(
  weight= 2,
  stroke = TRUE,
  fillOpacity = .65,
  data=counties,
  color = ~palette(progress),
   popup = ~paste("<strong>County:</strong>",NAME,
                   "<br>",
                   "<strong>Total Responses:</strong>",sumByCounty,
                  "<br>",
                   "<strong>Complete:</strong>",progress,"<strong>%</strong>")
  ) %>% addLegend(title = "Response <br> Goal Met", pal = palette, values = counties@data$progress, bins=5, opacity = 1, position="topright", labFormat = labelFormat(suffix = '%'))

Answer 1

创建一个具有两个环的多边形，第一个环具有整个地球的几何图形（或视图的边界），第二个环具有加利福尼亚的几何图形：

[
    // World
    [[90,-180], [90,180], [-90,180], [-90,-180]],
    // California
    [[42.006186,-123.233256],[42.011663,-122.378853],[41.995232,-121.037003],[41.995232,-120.001861],[40.264519,-119.996384],[38.999346,-120.001861],[38.101128,-118.71478],[37.21934,-117.498899],[36.501861,-116.540435],[35.970598,-115.85034],[35.00118,-114.634459],[34.87521,-114.634459],[34.710902,-114.470151],[34.448009,-114.333228],[34.305608,-114.136058],[34.174162,-114.256551],[34.108438,-114.415382],[33.933176,-114.535874],[33.697668,-114.497536],[33.54979,-114.524921],[33.40739,-114.727567],[33.034958,-114.661844],[33.029481,-114.524921],[32.843265,-114.470151],[32.755634,-114.524921],[32.717295,-114.72209],[32.624187,-116.04751],[32.536556,-117.126467],[32.668003,-117.24696],[32.876127,-117.252437],[33.122589,-117.329114],[33.297851,-117.471515],[33.538836,-117.7837],[33.763391,-118.183517],[33.703145,-118.260194],[33.741483,-118.413548],[33.840068,-118.391641],[34.042715,-118.566903],[33.998899,-118.802411],[34.146777,-119.218659],[34.26727,-119.278905],[34.415147,-119.558229],[34.40967,-119.875891],[34.475393,-120.138784],[34.448009,-120.472878],[34.579455,-120.64814],[34.858779,-120.609801],[34.902595,-120.670048],[35.099764,-120.631709],[35.247642,-120.894602],[35.450289,-120.905556],[35.461243,-121.004141],[35.636505,-121.168449],[35.674843,-121.283465],[35.784382,-121.332757],[36.195153,-121.716143],[36.315645,-121.896882],[36.638785,-121.935221],[36.6114,-121.858544],[36.803093,-121.787344],[36.978355,-121.929744],[36.956447,-122.105006],[37.115279,-122.335038],[37.241248,-122.417192],[37.361741,-122.400761],[37.520572,-122.515777],[37.783465,-122.515777],[37.783465,-122.329561],[38.15042,-122.406238],[38.112082,-122.488392],[37.931343,-122.504823],[37.893004,-122.701993],[38.029928,-122.937501],[38.265436,-122.97584],[38.451652,-123.129194],[38.566668,-123.331841],[38.698114,-123.44138],[38.95553,-123.737134],[39.032208,-123.687842],[39.366301,-123.824765],[39.552517,-123.764519],[39.831841,-123.85215],[40.105688,-124.109566],[40.259042,-124.361506],[40.439781,-124.410798],[40.877937,-124.158859],[41.025814,-124.109566],[41.14083,-124.158859],[41.442061,-124.065751],[41.715908,-124.147905],[41.781632,-124.257444],[42.000709,-124.213628],[42.006186,-123.233256]]
]

Plunker示例：http://embed.plnkr.co/ZWzuxz/preview