README.md

Shiny app to highlight on a Leaflet map by brushing a Plotly chart. Run for yourself with (provided all of the packages are installed):

shiny::runGist('da941dac84f730adcdde')

To get this to work on another dataset, you're going to need to have a sequential ID variable that matches the pointNumber column in the data frame generated by Plotly's event_data. See the setup.R script for how this was derived.

app.R

library(shiny)
library(leaflet)
library(plotly)
library(ggplot2)
library(geojsonio)

tarrxy <- geojson_read('tarrxy.geojson', what = 'sp')

ui <- fluidPage(
   
   titlePanel("Linked brushing with Plotly and Leaflet in Shiny"),
   
   fixedRow(
     column(width = 6, 
            plotlyOutput('scatter'))
   ), 
   
   fixedRow(
     column(width = 6, 
            leafletOutput('map'))
   )
   
)


server <- function(input, output, session) {
  
  output$scatter <- renderPlotly({
    
    g <- ggplot(tarrxy@data, aes(x = pctwhite, y = pctrep)) + 
      geom_point() + 
      xlab('Percent non-Hispanic white, 2010') +
      ylab('Percent voting Republican, 2012')
    
    ggplotly(g, source = 'source') %>% layout(dragmode = 'lasso')
    
  })
  
  selected_precincts <- reactive({
    
    eventdata <- event_data('plotly_selected', source = 'source')
    
    precincts <- as.numeric(eventdata[['pointNumber']])
    
    sub <- tarrxy[tarrxy$id %in% precincts, ]
    
    return(sub)
    
  })
  
   output$map <- renderLeaflet({

     tarrant_map <- leaflet() %>%
       addProviderTiles('CartoDB.DarkMatter') %>%
       addPolygons(data = tarrxy, weight = 1, smoothFactor = 0.2,
                    color = 'white', fillColor = 'grey') %>%
       addPolygons(data = selected_precincts(), fill = FALSE, color = '#FFFF00',
                   opacity = 1)

     tarrant_map

   })
}

shinyApp(ui = ui, server = server)

setup.R

library(rgdal)
library(rmapshaper)
library(geojsonio)

tarr <- readOGR(dsn = '.', layer = 'tarrant_precincts')

tarr_simp <- ms_simplify(tarr)

tarrxy <- spTransform(tarr_simp, CRS("+proj=longlat +datum=WGS84"))

tarrxy <- tarrxy[tarrxy$pctrep != -1 & tarrxy$pctwhite != -1, ]

l1 <- length(tarrxy) - 1

tarrxy$id <- 0:l1

geojson_write(tarrxy, file = 'tarrxy.geojson')

tarrxy.geojson

Nice work @walkerke! Since some of these packages are not on CRAN, it'd be useful to have code to install them in the README

Also, would it be possible to include code for obtaining the shapefile?

Thanks! And thanks for the feedback. I didn't use R to obtain and prep the shapefile but I'll include some pointers.

My ultimate goal is to get the Plotly events talking to leafletProxy so that the entire map doesn't re-load every time, and that the selected tracts are simply removed and then re-added - this isn't working for me just yet.