R中自定义标记的传单传说

Question

我有一个R Shiny应用程序，它使用Leaflet创建交互式地图。在此地图上，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。

我想要做的是在图中添加一个图例，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/如果它可以翻译成在R中工作。任何人都知道如何实现这一目标？

一个基本可重复的例子：

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（）中使用了图标not currently implemented，但是Yihui建议使用addControl（），使用原始的html - 这非常有效！

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'>green<br/>
<img src='http://leafletjs.com/docs/images/leaf-red.png'>red"

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

产生：

Answer 2

回应上述评论：无论您定义的初始尺寸如何，都可以更改图例中图标的大小。您所要做的就是添加

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

具体来说，您的代码需要：

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")