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I am attempting to make a choropleth using leaflet. I downloaded a shapefile of ZCTAs from data.gov and imported it into R via readOGR. Then, when piping that file into leaflet, nothing happens.

I think the issue may be that the lats and lons from the shapefile are being imported as factors instead of numerics? Except when I try to convert those variables into numerics, I am returned with the error:

Error in `$<-.data.frame`(`*tmp*', lat, value = numeric(0)) : replacement has 0 rows, data has 33144

On the other hand, that is only a guess and I am brand new to leaflet and mapping in general; I am still learning which way is up.

Here is my code:

shape <- readOGR(dsn = path.expand("//cifs2/radonfin$/MaxG/In Progress/Geographical Capture/Shape Files"), 
                 layer = "tl_2018_us_zcta510")
    shape@data$GEOID10 = as.numeric(as.character(shape@data$GEOID10))
    colnames(shp_Patients_by_ZCTA)[colnames(shp_Patients_by_ZCTA)=="INTPTLAT10"] <- "lat"
    colnames(shp_Patients_by_ZCTA)[colnames(shp_Patients_by_ZCTA)=="INTPTLON10"] <- "lng"

shape %>%
    leaflet(options = leafletOptions( minZoom = 8,
                                      maxZoom = 12,
                                      dragging = TRUE))  %>% 
        addProviderTiles("CartoDB.PositronNoLabels", group = "Light Mode")  %>%
        addProviderTiles("CartoDB.DarkMatterNoLabels", group = "Dark Mode") %>%
            addPolygons() %>%
                setView(lng = -71.808206, lat = 42.016621, zoom = 8) %>%
                    setMaxBounds(lng1 = -73.561893,
                                 lat1 = 42.855596,
                                 lng2 = -69.889730,
                                 lat2 = 41.001180) %>%
                        addMarkers(data = Hospital_Locations, 
                                   lat = Hospital_Locations$Latitude, 
                                   lng = Hospital_Locations$Longitude, 
                                   label = Hospital_Locations$Location) %>%
                            addLayersControl(baseGroups = c("Light Mode", "Dark Mode"), 
                                             overlayGroups = c("Boston", "Mansfield", "Milford", "Saint Anne's"))

My expect result is a leaflet map with the polygons described by the shapefile, but the actual results are that either:

  1. I get an error when converting lat and lon into numerics; or if I skip that,

  2. R freezes until I stop the code.

I really appreciate any help you can lend!!

CATSandCATSandCATS
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    I'm able to produce a choropleth without issue. I didn't include the `addMarkers` portion of the code since the data `Hospital_Locations` isn't provided in your example. Also, I ignored the 2 `colnames` lines since `shp_Patients_by_ZCTA` also isn't available. See if you can generate the choropleth without those lines first – astrofunkswag May 09 '19 at 20:12
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    Also I strongly recommend subsetting your data especially if you're limiting the map view to a portion of the US. Plotting 33,144 polygons is a lot for R to handle – astrofunkswag May 09 '19 at 20:13
  • I appreciate it. I redownloaded the data and took out the `colnames` and it is no longer causing errors . Now, the plot viewer just shows a blank white screen. Something else to figure out... But, how do I go about subsetting my data? I am trying to include MA, CT, and RI only. – CATSandCATSandCATS May 09 '19 at 20:26
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    You could lookup zip code prefixes and subset by say the `substr` of the `ZCTA5CE10` column – astrofunkswag May 09 '19 at 20:34
  • I appreciate it. I will give it a whirl and report back. – CATSandCATSandCATS May 09 '19 at 20:34

0 Answers0