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r - Shiny Web 应用程序中的传单不显示地图

问题描述

我试图创建一个交互式地图，允许用户通过使用以下 UI 功能和服务器功能对 census.gov 中的 shapefile 进行子集化来选择他们想要查找的州：

library(shiny)
library(leaflet)
library(magrittr)
library(rgdal)

shinyUI(fluidPage(
    
    titlePanel("JHU COVID-19 Modeling Visualization Map"),
    
    sidebarLayout(
        sidebarPanel(
            checkboxGroupInput("statesInput", "Choose the State(s)", 
                               c("AL", "MO", "AK", "MT", "AZ", "NE", 
                                 "AR", "NV", "CA", "NH", "CO", "NJ", 
                                 "CT", "NM", "DE", "NY", "DC", "NC", 
                                 "FL", "ND", "GA", "OH", "HI", "OK", 
                                 "ID", "OR", "IL", "PA", "IN", "RI", 
                                 "IA", "SC", "KS", "SD", "KY", "TN", 
                                 "LA", "TX", "ME", "UT", "MD", "VT", 
                                 "MA", "VA", "MI", "WA", "MN", "WV", 
                                 "MS", "WI", "WY")),
            
            submitButton("Submit")
        ),
        
        mainPanel(
            tabsetPanel(type = "tabs",
                        tabPanel("Map By State", leafletOutput("statePolygonMap"))
            )
        )
    )))

shinyServer(function(input, output) {
    dir <- getwd();
    
    statepolygonZip <- download.file("https://www2.census.gov/geo/tiger/GENZ2018/shp/cb_2018_us_state_500k.zip", 
                                     destfile = "cb_2018_us_state_500k.zip");
    unzip("cb_2018_us_state_500k.zip");
    statePolygonData <- readOGR("cb_2018_us_state_500k.shp", layer = "cb_2018_us_state_500k", 
                                GDAL1_integer64_policy = TRUE);
    ## obtaning the state shape file data provided by cencus.gov 
    ## for more categories of region shape file: 
    ## https://www.census.gov/geographies/mapping-files/time-series/geo/carto-boundary-file.html
    
    
    output$statePolygonMap <-renderLeaflet ({
        neStates <- paste(input$statesInput, collapse = ", ");
        ## extracting the all inputs and combining to a string 
        statesAbbr <- subset(statePolygonData, statePolygonData$STUSPS %in% c(neStates));
        ## subsetting the shape file with the selected states
        
        leaflet(statesAbbr) %>%
            addPolygons(color = "#444444", weight = 1, smoothFactor = 0.5,
                        opacity = 1.0, fillOpacity = 0.5,
                        fillColor = ~colorQuantile("YlOrRd", ALAND)(ALAND),
                        highlightOptions = highlightOptions(color = "white", weight = 2,
                                                            bringToFront = TRUE))
    })
    ## producing the map with polygon boundary on the state level
})

但是，输出没有在显示窗口上显示任何地图，而其他部分正常运行，没有错误但有一些警告： 显示窗口的屏幕截图

Warning in polygonData.SpatialPolygonsDataFrame(data) :
  Empty SpatialPolygonsDataFrame object passed and will be skipped
Warning in polygonData.SpatialPolygonsDataFrame(data) :
  Empty SpatialPolygonsDataFrame object passed and will be skipped

标签： rshinyleafletshapefiler-leaflet

解决方案

问题似乎与传单没有任何关系。问题似乎出在这些行中

neStates <- paste(input$statesInput, collapse = ", ");
statesAbbr <- subset(statePolygonData, statePolygonData$STUSPS %in% c(neStates));

当你paste0(collapse=)值时，你将一个值向量变成一个单一的 stinrg。例如

states <- c("AL", "MO")
paste0(states, collapse=",")
[1] "AL,MO"

但是，%in%运算符在向量中查找完全匹配，而不是逗号分隔的字符串。看

"AL" %in% "AL,MO"
# [1] FALSE
"AL" %in% c("AL", "MO")
# [1] TRUE

这意味着你真的应该只是使用

statesAbbr <- subset(statePolygonData, statePolygonData$STUSPS %in% input$statesInput);

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