Change google maps heatmap options in shiny - r

Question

I am using googleway library in Shiny R.
The heatmap displays correctly, but I cannot change the heatmap options. If I uncomment the block code where I try to change options, the app crashes.
Here is the part of the code that works, with the offending lines commented out.
library(googleway)
library(magrittr)
library(shiny)
library(shinydashboard)
# Define UI for app
header1 <- dashboardHeader(
title = "My Dashboard"
)
sidebar1 <- dashboardSidebar(
sidebarMenu(
fileInput("file0", "Choose CSV File",
multiple = TRUE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",".csv")),
sliderInput("opacity", "Opacity:",
min = 0, max = 1,
value = 0.5, step = 0.05),
sliderInput("radius", "Radius:",
min = 0, max = 50,
value = 25),
sliderInput("blur", "Blur:",
min = 0, max = 1,
value = 0.75, step = 0.05),
sliderInput("maxvalue", "MaxValue:",
min = 0, max = 1,
value = 1, step = 0.05)
) #sidebarMenu
) #dashboardSidebar
body1 <- dashboardBody(
fluidRow(
tabBox(
title = "TabBox Title 1",
id = "tabset1", height = "400px", width = 11,
selected = "Tab1",
tabPanel("Tab1",
google_mapOutput("Map1")
),
tabPanel("Tab2", "Tab content 2")
) #box
) #fluidRow
) #dashboardBody
ui <- dashboardPage(header1, sidebar1, body1)
# Define data
df <- data.frame(lat = c(14.61),
lon = c(-90.54),
weight = c(100))
# Define SERVER logic
server <- function(input, output, session) {
map_key <- "my_key"
## https://developers.google.com/maps/documentation/javascript/get-api-key
## plot the map
output$Map1 <- renderGoogle_map({
google_map(key = map_key, data = df, zoom = 2, search_box = F) %>%
add_heatmap(weight = "weight") #%>%
#add_traffic()
}) #renderGoogle_map
observeEvent(input$opacity, {
# THIS PART IS COMMENTED OUT BECAUSE THE APP CRASHES
# google_map_update(map_id = "Map1") %>%
# update_heatmap(data = df, option_opacity = input$opacity)
}) #observeEvent
} #server
# Run app
shinyApp(ui, server)
Your help with this will be greatly appreciated! :)

Answer 1

You can use a reactive({}) to carry the input$opacity value and pass it directly to add_heatmap() to achieve the opacity responsiveness.
This can still be done inside the google_map_update(), but you'd have to clear the heatmap layer first, otherwise you'd just be adding layers on top of each other.
server <- function(input, output, session) {
map_key <- "your_key"
## https://developers.google.com/maps/documentation/javascript/get-api-key
opacity <- reactive({
return(input$opacity)
})
## plot the map
output$Map1 <- renderGoogle_map({
google_map(key = map_key, data = df, zoom = 2, search_box = F) %>%
add_heatmap(weight = "weight") #%>%
#add_traffic()
}) #renderGoogle_map
observeEvent(input$opacity, {
google_map_update(map_id = "Map1") %>%
clear_heatmap() %>%
add_heatmap(data = df, option_opacity = opacity())
})
}
} #server