R中自定义标记的传单图例

Question

我有一个使用 Leaflet 创建交互式地图的 R Shiny 应用程序。在这张地图上，分类变量用于指定不同类型的点，并使用自定义标记（不同的图标，取决于因子级别）进行可视化。

我想做的是在情节中添加一个图例，但让图例显示各种标记图标而不是纯色。 legends tutorial 不包含此内容。

我遇到了另一个 SO answer that seems to solve this - 但它是用 JavaScript 完成的，我不知道如何翻译它/是否可以翻译成在 R 中工作。有人知道如何完成这个吗？

一个基本的可重现示例：

library(leaflet)

# Sample Data
data(quakes)
quakes <- quakes[1:10,]

# Choose Icon:
leafIcons <- icons(
  iconUrl = ifelse(quakes$mag < 4.6,
                   "http://leafletjs.com/docs/images/leaf-green.png",
                   "http://leafletjs.com/docs/images/leaf-red.png"
  ),
  iconWidth = 38, iconHeight = 95,
  iconAnchorX = 22, iconAnchorY = 94)

# Produce Map:
leaflet(data = quakes) %>% addTiles() %>%
  addMarkers(~long, ~lat, icon = leafIcons)

Answer 1

虽然在 addLegend() 中使用的图标是 not currently implemented，但易辉建议使用 addControl()，使用原始 html - 效果很好！

library(leaflet)

# Sample Data
data(quakes)
quakes <- quakes[1:10,]

# Choose Icon:
leafIcons <- icons(
  iconUrl = ifelse(quakes$mag < 4.6,
                   "http://leafletjs.com/examples/custom-icons/leaf-green.png",
                   "http://leafletjs.com/examples/custom-icons/leaf-red.png"
  ),
  iconWidth = 38, iconHeight = 95,
  iconAnchorX = 22, iconAnchorY = 94)

html_legend <- "<img src='http://leafletjs.com/examples/custom-icons/leaf-green.png'>green<br/>
<img src='http://leafletjs.com/examples/custom-icons/leaf-red.png'>red"

# Produce Map:
leaflet(data = quakes) %>% addTiles() %>%
  addMarkers(~long, ~lat, icon = leafIcons) %>%
  addControl(html = html_legend, position = "bottomleft")

链接

• 绿色：http://leafletjs.com/examples/custom-icons/leaf-green.png
• 红色：http://leafletjs.com/examples/custom-icons/leaf-red.png
• 橙色：http://leafletjs.com/examples/custom-icons/leaf-orange.png

产生：

Answer 2

回应上面的评论：你可以改变图例中图标的大小，不管你定义的初始大小。你所要做的就是添加

style='width:(desired_width)px;height:(desired_height)px'; 到 HTML 部分。

具体来说，您的代码希望：

library(leaflet)

# Sample Data
data(quakes)
quakes <- quakes[1:10,]

# Choose Icon:
leafIcons <- icons(
iconUrl = ifelse(quakes$mag < 4.6,
               "http://leafletjs.com/docs/images/leaf-green.png",
               "http://leafletjs.com/docs/images/leaf-red.png"
  ),
  iconWidth = 38, iconHeight = 95,
  iconAnchorX = 22, iconAnchorY = 94)

html_legend <- "<img src='http://leafletjs.com/docs/images/leaf-green.png'
style='width:10px;height:10px;'>green<br/> 

<img src='http://leafletjs.com/docs/images/leaf-red.png'  
style='width:10px;height:10px;'>red"

# Produce Map:
leaflet(data = quakes) %>% addTiles() %>%
addMarkers(~long, ~lat, icon = leafIcons) %>%
addControl(html = html_legend, position = "bottomleft")