How do I save addDrawToolbar shapes drawn in an R Leaflet Shiny map so I can re-import them?

Question

I need to take the shapes drawn in an R Leaflet Shiny app using addDrawToolbar in leaflet.extras and save them to a file that can be re-imported by an R Leaflet Shiny app at a later time.

I am focusing on the leaflet.extras information in GitHub by Bhaskar Karambelkar where it lists the commands to pull out the data for the shapes drawn. How do I parse out this data in R?

The following code is what I can do so far: Draw shapes and print them out as a .csv or .txt file. I've included both examples. So in this code, you draw whatever shapes you want from the Draw Toolbar and then hit the Generate Shape List button.

It works for capturing all the shape coordinates, but in these formats the data is not as usable as I need them to be. Is there a way to parse this data so that it can be re-imported, displayed, and edited if need be? Any insights on this is really appreciated!

library(shiny)
library(leaflet)
library(leaflet.extras)
library(utils)

sh <- data.frame()

ui <- bootstrapPage(
    tags$style(type = "text/css", "html, body {width:100%;height:100%}"),
    leafletOutput("mymap", width = "100%", height = "100%"),
    absolutePanel(top = 10, right = 10, width = 300,
                  style = "padding: 8px",
                  actionButton("printShapes", h5(strong("Generate Shape List")))
    )
)

server <- function(input, output, session) {
    
    output$mymap <- renderLeaflet({
        leaflet() %>%
            addTiles(group = "Default", attribution = 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors') %>%
            setView(lng = -98, lat = 38, zoom = 4) %>%
            addDrawToolbar(targetGroup = "draw", position = "topleft", editOptions = editToolbarOptions(edit=TRUE))
    })
    
    # Generate Shape List Action Button
    observeEvent(input$printShapes, {
        shapedf <- data.frame()
        reactive(shapedf)                       
        shapedf <-input$mymap_draw_all_features  
        sh <<- as.data.frame(shapedf)           
        sh <- t(sh)                             
        shpwrite <- write.csv(sh, paste0("OUTPUTdrawings",".csv"))
        shpwrite1 <- dput(sh, file = "OUTPUTdrawings1.txt")
    })
}

shinyApp(ui = ui, server = server)

megatronFencer · Accepted Answer · 2021-04-08T22:12:12.677

After much cogitation, angst, trial and error, I finally figured out how to do this. Not sure if this is the best way to do this, but it works.

library(shiny)
library(leaflet)
library(leaflet.extras)
library(utils)

sh <- data.frame()

ui <- bootstrapPage(
    tags$style(type = "text/css", "html, body {width:100%;height:100%}"),
    leafletOutput("mymap", width = "100%", height = "100%"),
    absolutePanel(top = 10, right = 10, width = 300,
                  style = "padding: 8px",
                  fileInput("drawingFile",h4(strong("Input Drawing CSV")), accept = ".csv"),
                  actionButton("printShapes", h5(strong("Generate Drawing File")))
    )
)

server <- function(input, output, session) {
    
    output$mymap <- renderLeaflet({
        leaflet() %>%
            addTiles(group = "Default", attribution = 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors') %>%
            setView(lng = -98, lat = 30, zoom = 4) %>%
            addDrawToolbar(targetGroup = "draw", position = "topleft", editOptions = editToolbarOptions(edit=TRUE))
    })
    
    # Generate Shape List Action Button
    observeEvent(input$printShapes, {
        shapedf <- data.frame()
        reactive(shapedf)
        shapedf <-input$mymap_draw_all_features
        sh <<- as.data.frame(shapedf)
        
        # sh <- t(sh) # This is easier to read manually, but not for reading into R.
        shpwrite <- write.csv(sh,paste0("Drawings", ".csv"))
    })
    
    # Intake Shape CSV
    observeEvent(input$drawingFile, {
        drawFile <- input$drawingFile
        ext <- file_ext(drawFile$datapath)
        req(drawFile)
        validate(need(ext == "csv", "Please upload a csv file."))
        
        ddf <- read.csv(drawFile$datapath, header = TRUE) # The drawing dataframe
        ind <- which(ddf == "Feature") # Index for drawing df to break up the df to redraw the shapes.
        ind <- as.array(ind)
        
        for (i in 1:nrow(ind)) {
            if(i != nrow(ind)) thisShape <- ddf[ind[i]:ind[i+1]]
            else thisShape <- ddf[ind[i]:ncol(ddf)]
            
            #####
            if(thisShape[3] == "polyline") {
                tf <- array(startsWith(names(thisShape),"features.geometry.coordinates"))
                w <- 1
                pnts <- array()
                for (i in 1:nrow(tf)) {
                    if(tf[i] == TRUE) {
                        pnts[w] <- thisShape[i]
                        w <- w+1
                    }
                }
                n <- 1
                m <- 1
                plng <- array()
                plat <- array()
                pnts <- as.array(pnts)
                for (j in 1:nrow(pnts)) {
                    if(j %% 2 == 1) {
                        plng[n] <- pnts[j]
                        n <- n+1
                    }
                    else if(j %% 2 == 0) {
                        plat[m] <- pnts[j]
                        m <- m+1
                    }
                }
                as.vector(plng, mode = "any")
                as.vector(plat, mode = "any")
                PL <- data.frame(matrix(unlist(plng)))
                PLsub <- data.frame(matrix(unlist(plat)))
                PL <- cbind(PL, PLsub)
                colnames(PL) <- c("lng","lat")
                PL1 <- reactiveVal(PL)
                
                proxy <- leafletProxy("mymap", data = PL1())
                proxy %>% addPolylines(lng = ~lng, lat = ~lat, group = "draw")
            }
            #####
            else if(thisShape[3] == "polygon") {
                tf <- array(startsWith(names(thisShape),"features.geometry.coordinates"))
                w <- 1
                pnts <- array()
                for (i in 1:nrow(tf)) {
                    if(tf[i] == TRUE) {
                        pnts[w] <- thisShape[i]
                        w <- w+1
                    }
                }
                n <- 1
                m <- 1
                plng <- array()
                plat <- array()
                pnts <- as.array(pnts)
                for (j in 1:nrow(pnts)) {
                    if(j %% 2 == 1) {
                        plng[n] <- pnts[j]
                        n <- n+1
                    }
                    else if(j %% 2 == 0) {
                        plat[m] <- pnts[j]
                        m <- m+1
                    }
                }
                as.vector(plng, mode = "any")
                as.vector(plat, mode = "any")
                PG <- data.frame(matrix(unlist(plng)))
                PGsub <- data.frame(matrix(unlist(plat)))
                PG <- cbind(PG, PGsub)
                colnames(PG) <- c("lng","lat")
                PG1 <- reactiveVal(PG)
                
                proxy <- leafletProxy("mymap", data = PG1())
                proxy %>% addPolygons(lng = ~lng, lat = ~lat, group = "draw")
            }
            #####
            else if(thisShape[3] == "rectangle"){
                rlng1 <- as.numeric(thisShape[5])
                rlat1 <- as.numeric(thisShape[6])
                rlng2 <- as.numeric(thisShape[9])
                rlat2 <- as.numeric(thisShape[10])
                
                proxy <- leafletProxy("mymap")
                proxy %>% addRectangles(lng1 = rlng1, lat1 = rlat1, lng2 = rlng2, lat2 = rlat2,
                                        group = "draw")
            }
            #####
            else if(thisShape[3] == "circle"){
                crad <- as.numeric(thisShape[4])
                clng <- as.numeric(thisShape[6])
                clat <- as.numeric(thisShape[7])
                
                proxy <- leafletProxy("mymap")
                proxy %>% addCircles(lng = clng, lat = clat, radius = crad, group = "draw")
            }
            #####
            else if(thisShape[3] == "marker") {
                mlng <- as.numeric(thisShape[5])
                mlat <- as.numeric(thisShape[6])
                
                proxy <- leafletProxy("mymap")
                proxy %>% addMarkers(lng = mlng, lat = mlat, group = "draw")
            }
            #####
            else if(thisShape[3] == "circlemarker") {
                cmlng <- as.numeric(thisShape[6])
                cmlat <- as.numeric(thisShape[7])
                
                proxy <- leafletProxy("mymap")
                proxy %>% addCircleMarkers(lng = cmlng, lat = cmlat, group = "draw")
            }
        }
    })
}

shinyApp(ui = ui, server = server)

How do I save addDrawToolbar shapes drawn in an R Leaflet Shiny map so I can re-import them?

1 Answers1