R - 被动过滤数据以生成地图

Question

在使用mapview处理闪亮的地图时，我被反应器弄糊涂了，并试图让我的地图动态更新。这是一个可重现的示例，尽管它是使用其他 SO 答案中的原理设计的，但它无法正常工作：

#
# This is a Shiny web application. You can run the application by clicking
# the 'Run App' button above.
#
# Find out more about building applications with Shiny here:
#
#    http://shiny.rstudio.com/
#
library(shiny)
library(sf)
library(mapview)
# Define UI for application that draws a histogram
ui <- fluidPage(
# Application title
titlePanel("Test of Mapview Selective Viewing"),
# Sidebar with a slider input for number of bins 
sidebarLayout(
sidebarPanel(
selectInput("county", "County Name",
choices = c("All", levels(franconia$NAME_ASCI)),
selected = "All"
)
),
# Show a plot of the generated distribution
mainPanel(
mapviewOutput("mapPlot")
)
)
)
# Define server logic required to draw a histogram
server <- function(input, output) {
fran <- reactive({
f <- franconia
if(input$county != "All") f <- franconia %>% filter(NAME_ASCI == input$county)
f
})
output$mapPlot <- renderMapview({
#get the data
f <- isolate(fran())
#generate a map
mapview(f, zcol = "NAME_ASCI")
})
}
# Run the application 
shinyApp(ui = ui, server = server)

这有效，但地图不会更新。我尝试放入一个操作按钮 - 并将input$button放在隔离语句之前，但是，这会导致整个事情抛出错误。

我想要么看到所有东西，要么看到一个县。

关于这里缺少/错误的任何想法？我对闪亮和处理反应有点陌生！

Answer 1

使用renderMapview似乎在某种程度上"不鼓励"(见 https://github.com/r-spatial/mapview/issues/160#issuecomment-398130788; https://github.com/r-spatial/mapview/issues/58(。应改为对mapview对象的 @map 属性使用renderLeaflet。这应该有效：

library(shiny)
library(sf)
library(mapview)
library(leaflet)
# Define UI for application that draws a histogram
ui <- fluidPage(

# Application title
titlePanel("Test of Mapview Selective Viewing"),

# Sidebar with a slider input for number of bins 
sidebarLayout(
sidebarPanel(
selectInput("county", "County Name",
choices = c("All", levels(franconia$NAME_ASCI)),
selected = "All"
)

),

# Show a plot of the generated distribution
mainPanel(
mapviewOutput("mapPlot")
)
)
)
# Define server logic required to draw a histogram
server <- function(input, output) {

fran <- reactive({
f <- franconia
if(input$county != "All") f <-  f <- franconia[franconia$NAME_ASCI == input$county, ] 

f
})

output$mapPlot <- renderLeaflet({

#get the data
f <- fran()

#generate a map
mapview(f, zcol = "NAME_ASCI")@map
})
}
# Run the application 
shinyApp(ui = ui, server = server)

(请注意，我还必须按照@Kent Johnson的建议删除isolate电话(

哼！

Answer 2

将地图输出放在observe内并摆脱isolate。isolate阻止更新，observe允许您将其删除：

observe({
output$mapPlot <- renderMapview({
f <- fran()
mapview(f, zcol = "NAME_ASCI")
})
})

Answer 3

通常，您不应该将渲染输出嵌套在观察器中，您可以像这样拆分它们：

mapPlot <- reactive(mapview(fran(), zcol = "NAME_ASCI"))
output$mapPlot <- renderMapview(mapPlot())

Answer 4

@ibusett是正确的，但这是包括子集在内的工作代码(他们的代码仅适用于输入== All(。

编辑：他们更新了他们的代码以匹配我的常规子集，但您可以在 sf 对象上使用 dplyr：：filter(正如他们提到的(。

library(sf)
library(mapview)
library(leaflet)
ui <- fluidPage(

# Application title
titlePanel("Test of Mapview Selective Viewing"),

# Sidebar with a slider input for number of bins 
sidebarLayout(
sidebarPanel(
selectInput("county", "County Name",
choices = c("All", levels(franconia$NAME_ASCI)),
selected = "All"
)

),

# Show a plot of the generated distribution
mainPanel(
mapviewOutput("mapPlot")
)
)
)
# Define server logic required to draw a histogram
server <- function(input, output) {

fran <- reactive({
f <- franconia
if(input$county != "All"){ 
f <- franconia[franconia$NAME_ASCI == input$county, ]
}

f
})

output$mapPlot <- renderLeaflet({

#get the data
f <- fran()

#generate a map
mapview(f, zcol = "NAME_ASCI")@map
})
}
# Run the application 
shinyApp(ui = ui, server = server)