How do I fix an error regarding addPolygon() from leaflet

Question

I am currently struggling with spatial dataframes using leaflet to create interactive maps. in R I have been trying out many different solutions from multiple threads, but my addPolygon() does not seem to work at all. Can anyone help me trying to figure out what goes wrong? I have replicated my dataset in a simple format (def_rep) and the spatial data is on the state level for which I call tigris::states(). I then merge the dataframes into merged_df_rep and continue with setting up the leaflet(). But I always get the same error: Error in UseMethod("metaData") : no applicable method for 'metaData' applied to an object of class "c('sfc_MULTIPOLYGON', 'sfc')". Many thanks for any help or pointers as to what I am doing wrong!

Here is my code and an example df:

library(ggmap)
library(tidygeocoder)
library(tigris)
library(sf)
library(htmltools)
library(labelled)
library(leaflet) 
library(tidyverse)




NAME <- c("West Virginia", "Florida", "Illinois", "Minnesota","Maryland", "Rhode Island", "Idaho", "New Hampshire","North Carolina",       "Vermont", "Connecticut", "Delaware","New Mexico", "California", "New Jersey", "Wisconsin", "Oregon", "Nebraska","Pennsylvania","Washington",           "Louisiana", "Georgia", "Alabama" , "Utah","Ohio","Texas", "Colorado", "South Carolina","Oklahoma" , "Tennessee", "Wyoming", "Hawaii", "North Dakota", "Kentucky",  "Maine" , "New York", "Nevada" ,  "Alaska" , "Michigan", "Arkansas","Mississippi","Missouri", "Montana" ,"Kansas", "Indiana", "South Dakota","Massachusetts", "Virginia", "District of Columbia", "Iowa","Arizona")
values <- c(1000:1050)

df_rep <- data.frame(NAME, values)

map_df <- states()



problems <- anti_join(map_df,df_rep, by = "NAME")
head(problems[,1:7])


###dropping the problems

map_df_clean<-map_df[!(map_df$NAME=="United States Virgin Islands" | map_df$NAME=="Commonwealth of the Northern Mariana Islands"| map_df$NAME=="Guam"| map_df$NAME=="Puerto Rico"| map_df$NAME=="American Samoa"),]



merged_df_rep <- left_join(map_df_clean, df_rep, by = "NAME")

##try to transform the data
merged_df_rep <- st_transform(merged_df_rep, "+proj=longlat +datum=WGS84")


pal <- colorNumeric("Greens", domain = merged_df_rep$values) ##create a color palette

#states_merged_df <- sf::as_Spatial(states_merged_df)

popup_sb <- paste0("Total values for" ,merged_df_rep$NAME, "Number:", as.character(merged_df_rep$values)) ##create the correct popup

merged_df_rep %>% 
leaflet() %>% 
  addProviderTiles("CartoDB.Positron") %>% 
  setView(~-98.483330,38, .712046, zoom = 4) %>% 
  addPolygons(
    data = merged_df_rep$geometry,
              fillColor = ~pal(merged_df_us_1$n_response),
              fillOpacity = .7,
              weight = .2, 
              smoothFactor = .2,
              popup = ~popup_sb) %>% 
  addLegend(pal = pal, 
            values = merged_df_rep$values,
            position = "bottomright",
            title = "Responses")

score 0 · Answer 1 · answered Dec 20 '22 at 10:54

First of all, you haven't provided us merged_df_us_1$n_response therefore I have commented out fillColor, secondly there is an error in

setView(~-98.483330,38, .712046, zoom = 4) %>%

and the third thing is, you can't provide just geometry column as a data, when leaflet expects an sf object:

data = merged_df_rep$geometry,

merged_df_rep %>%
  leaflet() %>%
  addProviderTiles("CartoDB.Positron") %>%
  setView(-98.483330, 38.712046, zoom = 4) %>%
  addPolygons(
    data = merged_df_rep,
    #    fillColor = ~pal(merged_df_us_1$n_response),
    fillOpacity = .7,
    weight = .2,
    smoothFactor = .2,
    popup = ~popup_sb
  ) %>%
  addLegend(
    pal = pal,
    values = merged_df_rep$values,
    position = "bottomright",
    title = "Responses"
  )

Regards, Grzegorz

margusl · Answer 2 · 2022-12-20T11:03:27.180

The error states that something can't handle sfc class, sfc is geometry column of simple features or merged_df_rep$geometry in this case. Just data = merged_df_rep would have worked, but as you allready pipe the sf object to leaflet() and setting its default default data object, there's no need to override it with same dataset in individual layers.

There also seems to be some confusion regarding formula interface and that part of leaflet can indeed be bit confusing, but it's mostly used to reference variables of a dataset that was passed as a data parameter. You may want to revisit https://rstudio.github.io/leaflet/map_widget.html#the-formula-interface

library(tigris)
library(sf)
library(leaflet)
library(dplyr)

NAME <- c("West Virginia", "Florida", "Illinois", "Minnesota", "Maryland", "Rhode Island", "Idaho", "New Hampshire", "North Carolina", "Vermont", "Connecticut", "Delaware", "New Mexico", "California", "New Jersey", "Wisconsin", "Oregon", "Nebraska", "Pennsylvania", "Washington", "Louisiana", "Georgia", "Alabama", "Utah", "Ohio", "Texas", "Colorado", "South Carolina", "Oklahoma", "Tennessee", "Wyoming", "Hawaii", "North Dakota", "Kentucky", "Maine", "New York", "Nevada", "Alaska", "Michigan", "Arkansas", "Mississippi", "Missouri", "Montana", "Kansas", "Indiana", "South Dakota", "Massachusetts", "Virginia", "District of Columbia", "Iowa", "Arizona")
values <- c(1000:1050)
df_rep <- data.frame(NAME, values)

map_df <- states() %>% st_transform("WGS84")
merged_df_rep <- inner_join(map_df, df_rep, by = "NAME")

pal <- colorNumeric("Greens", domain = merged_df_rep$values) ## create a color palette

leaflet(merged_df_rep) %>%
  addProviderTiles("CartoDB.Positron") %>%
  setView(-98.483330, 38, .712046, zoom = 4) %>%
  addPolygons(
    fillColor = ~ pal(values),
    fillOpacity = .7,
    weight = .2,
    smoothFactor = .2,
    popup = ~ paste0("Total values for ", NAME, "<br> Number: ", as.character(values))
  ) %>%
  addLegend(
    pal = pal,
    values = ~values,
    position = "bottomright",
    title = "Responses"
  )

How do I fix an error regarding addPolygon() from leaflet

2 Answers2