reactive rasters leaflet/shiny

[Hugh Sturrock]

Hi all,

I"m trying to put together a shiny app with raster layers plotted over a leaflet map. The rasters are time series so I ahve a time slider to select which layer from a raster stack to plot. The code below works fine, but I'd like to use the reactive and leafletProxy functions to prevent the app from re-running the whole script (thereby resetting the setview, zoom and layers). But I can't work out how to script it. 

covariates <- stack(list.files(paste0(system.file(package="dismo"), '/ex'),

                               pattern='grd', full.names=TRUE))

map = leaflet() %>% addTiles('http://{s}.tiles.wmflabs.org/bw-mapnik/{z}/{x}/{y}.png',

                                    attribution = paste(

                                      '&copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors',

                                      '&copy; <a href="http://cartodb.com/attributions">CartoDB</a>'

                                    ))

shinyServer(function(input, output){

  

output$myMap = renderLeaflet({

  map %>% addRasterImage(covariates[[input%layer]])

})

})

# This is what I was trying but I've got it wrong..

shinyServer(function(input, output){

  

output$myMap = renderLeaflet({

  map

})

rasterReactive<-reactive({covariates[[input$layer]]})

observe({

  leafletProxy("myMap", data =rasterReactive()) %>%

  clearImages() %>% addRasterImage()

})

})

[Joe Cheng]

1) Remove data arg from leafletProxy
2) Pass raster to addRasterImage
3) Add a hard coded layerId to addRasterImage, otherwise you'll just keep adding more and more rasters to the map

Sorry for terseness, phone

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[Hugh Sturrock]

HI Joe,

Thanks! But I must be doing something wrong…Any ideas? code below

server.R

# download and load data

covariates <- stack(list.files(paste0(system.file(package="dismo"), '/ex'),
pattern='grd', full.names=TRUE))

map = leaflet() %>% addTiles('http://{s}.basemaps.cartocdn.com/dark_all/{z}/{x}/{y}.png',

attribution = paste(
'&copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors'

))

shinyServer(function(input, output){

output$raster_map = renderLeaflet({
map})

reactiveRaster <- reactive({covariates[[input$integer]]})

observe({
leafletProxy("raster_map") %>%
clearImages() %>%
addRasterImage(reactiveRaster)
})

})



UI.R

shinyUI(fluidPage(
sliderInput("integer", "Time period",
min=1, max=12, value=1, ticks=F),

mainPanel(leafletOutput('raster_map', width=1500,height=800))
)
)

[Joe Cheng]

There might be something else too, but addRasterImage(reactiveRaster) should be addRasterImage(reactiveRaster()).

[Hugh Sturrock]

Works! Thanks!

[prasenjit acharya]

Hi

I have been gone through the discussion in this post. It is an interesting post for the shiny users. However, I have been facing similar problem in shiny using raster image. Since I am new in shiny, I vehemently need your help to resolve this. Any suggestions are welcome. I am attaching the code below. 

rst <- raster('/home/prasenjit/Documents/prasenjit docs/ndvi_map.tif')

ui <- bootstrapPage(

  tags$style(type = "text/css", "html, body {width:100%;height:100%}"),

  leafletOutput("map", width = "100%", height = "100%"),

  absolutePanel(top = 10, right = 10,

                sliderInput("range", "ndvi", min(values(rst)), max(values(rst)),

                            value = range(values(rst)), step = 0.1)

                #checkboxInput("legend", "Show legend", TRUE)

  )

)

server <- function(input, output, session) {

  filteredData <- reactive({

    overlay(rst[[input$range]], fun = function(x){

      if(is.na() == T){x <- NA} else if(x >=input$range[1] && x <=input$range[2]){x*1} else(x <- NA)

  })

  })

  pal <- colorNumeric("RdYlBu", values(rst), 

                      na.color = "transparent")

  output$map <- renderLeaflet({

  leaflet() %>% addTiles() %>%

    addRasterImage(rst, colors = pal, opacity = 1) %>%

    addLegend(position = "bottomright", pal = pal, values = values(rst),

              opacity = 1)

    observe({

      leafletProxy("map") %>%

        clearImages() %>%

        addRasterImage(filteredData(), colors = pal, opacity = 1)

    })

  })

}

shinyApp(ui, server)

Listening on http://127.0.0.1:3292
Warning: Error in inherits: cannot use this formula, probably because it is not vectorized
  61: <Anonymous>