I have written code for inputs and a leaflet map that work independently, but error when I try to get them to be dependent on each other. Overall, I am trying to allow these 4 sliders to be adjusted to provide "weights" which are then used to calculate new fields in my Spatial Polygon Dataframe. I then want to take that updated file and put it into Leaflet. I then want to be able to further filter the polygons by score with another slider.
I have followed this RStudio Tutorial closely to format my code. Basically, I'm using reactive expressions to do my calculations, defining them as a variable (eg NewVar <- reactive({...})), and then trying to use that variable in subsequent code in the data argument (eg data = NewVar()). My code would error when I did that and also when I referred to columns with ~ (eg values = ~Column). But I couldn't refer to columns using $Column because it is a function now, not a Spatial Polygon DataFrame. I tried to fix this by, within the reactive function, assigning the function to a variable (eg SPDF <- NewVar()) and then using values = SPDF$Column. That is also erroring (Warning: Error in <-: invalid (NULL) left side of assignment) and (Warning: Error in : trying to get slot "data" from an object of a basic class ("numeric") with no slots).
I'm pasting the entire code below. Please do let me know if anything stands out - or to help me understand how to properly call on a column from a reactive expression that did calculations on a Spatial Polygon Dataframe.
# Build UI
ui <- fluidPage(
titlePanel("UNCWI Score Evaluation"),
sidebarLayout(
sidebarPanel(
sliderInput(inputId = "weightir", label = "Weight for IR",
value = 0.19, min = 0, max = 1),
sliderInput(inputId = "weightul", label = "Weight for Upland Protection",
value = 0.31, min = 0, max = 1),
sliderInput(inputId = "weightva", label = "Weight for Vulnerable Areas",
value = 0.21, min = 0, max = 1),
sliderInput(inputId = "weightwsc", label = "Weight for WSC",
value = 0.29, min = 0, max = 1),
actionButton("run", "Run")
),
mainPanel(
leafletOutput("map"),
sliderInput("range", "Scores", min = 0.0, max= 10.0, value = as.numeric(c("0.0", "10.0")), step = 0.1),
actionButton("export", "Export Shapefile")
)
))
# Render Outputs
server <- function(input, output) {
defaultData <- eventReactive(input$run, {
# Multiply by Weights
merge.proj@data$IR_WtScore <- round(merge.proj@data$MEAN_IR_Sc*input$weightir, digits = 1)
merge.proj@data$UL_WtScore <- round(merge.proj@data$MEAN_UL_Sc*input$weightul, digits = 1)
merge.proj@data$VA_WtScore <- round(merge.proj@data$MEAN_VA_Sc*input$weightva, digits = 1)
merge.proj@data$WSC_WtScore <- round(merge.proj@data$MEAN_WSC_S*input$weightwsc, digits = 1)
# Find Total Score
merge.proj@data$Total_Score <- merge.proj@data$IR_WtScore + merge.proj@data$UL_WtScore + merge.proj@data$VA_WtScore + merge.proj@data$WSC_WtScore
})
# Plot with leaflet
# Palette for map
colorpal <- reactive({
merge.proj <- defaultData()
colorNumeric(palette = "YlOrRd",
domain = merge.proj$Total_Score)
})
# Label Option for map
labels <- reactive({
merge.proj <- defaultData()
lsprintf("<strong>Parcel ID: </strong>%s<br/><strong>Total Score:</strong>%g", merge.proj$PARCEL_ID, merge.proj$Total_Score) %>% lapply(htmltools::HTML)
})
# Render Default Map
output$map <- renderLeaflet ({leaflet() %>%
merge.proj <- defaultData()
pal <- colorpal()
lab <- labels()
addTiles() %>%
addPolygons(data=merge.proj,
fillColor = ~pal(Total_Score),
weight = 1,
opacity = 1,
color = "white",
dashArray = "3",
fillOpacity = 0.7,
highlight = highlightOptions(
weight = 3,
color = "#666",
dashArray = "",
fillOpacity = 0.7,
bringToFront = TRUE),
label = lab,
labelOptions = labelOptions(
style = list("font-weight" = "normal", padding = "3px 8px"),
textsize = "15px",
direction = "auto")) %>%
addLegend(position = "bottomleft",pal = pal, opacity = 0.7, values = merge.proj$Total_Score, title = "<strong>Total Score</strong>")
})
# Update map to parcel score slider
# Subset data
filteredData <- reactive({
merge.proj <- defaultData()
merge.proj[merge.proj@data$Total_Score >= input$range[1] & merge.proj@data$Total_Score <= input$range[2],]
})
# New Palette
colorpal2 <- reactive({
merge.proj <- filteredData()
colorNumeric(palette = "YlOrRd",
domain = merge.proj$Total_Score)
})
# Label Option
labels2 <- reactive({
merge.proj <- filteredData()
sprintf("<strong>Parcel ID: </strong>%s<br/><strong>Total Score: </strong>%g", merge.proj$PARCEL_ID, merge.proj$Total_Score) %>% lapply(htmltools::HTML)
})
#Leaflet Proxy
observe({
merge.proj <- filteredData()
pal2 <- colorpal2()
lab2 <- labels2()
leafletProxy("map", data = filteredData()) %>%
clearShapes() %>%
addPolygons(
fillColor = ~pal2(Total_Score),
weight = 1,
opacity = 1,
color = "white",
dashArray = "3",
fillOpacity = 0.7,
highlight = highlightOptions(
weight = 3,
color = "#666",
dashArray = "",
fillOpacity = 0.7,
bringToFront = TRUE),
label = lab2,
labelOptions = labelOptions(
style = list("font-weight" = "normal", padding = "3px 8px"),
textsize = "15px",
direction = "auto"))
})
#Update Legend
observe({
proxy <- leafletProxy("map", data = filteredData())
pal2 <- colorpal2()
proxy %>% clearControls()
proxy %>% addLegend(position = "bottomleft",pal = pal2, opacity = 0.7, values = ~Total_Score, title = "<strong>Total Score</strong>")
})
# Export new shapefile
observeEvent(input$export, {
merge.proj <- filteredData()
writeOGR(merge.proj, dsn = "Data", layer = "UNCWI_Output", driver = "ESRI Shapefile")
})
}
shinyApp(ui = ui, server = server)
