This document contains code for building interactive Shiny apps with Leaflet maps. It defines user input controls to select a geographic region and location. Map layers are added and updated based on the user selections. Code is also included to zoom the map to the selected location bounds and identify the clicked feature.

2. > me
$name
[1] "Takashi Kitano"
$twitter
[1] "@kashitan"
$work_in
[1] " " %>% " "

9. glimpse(choices)
List of 4
$ : Named chr [1:58] "11101" "11102" "11103" "11104" ...
..- attr(*, "names")= chr [1:58] " " " " "
" " " ...
$ : Named chr [1:36] "12101" "12102" "12103" "12104" ...
..- attr(*, "names")= chr [1:36] " " " " "
" " " ...
$ : Named chr [1:51] "13101" "13102" "13103" "13104" ...
..- attr(*, "names")= chr [1:51] " " " " " " "
" ...

10. names(choices)
[1] " " " " " " " "
choices[[" "]]
"13101" "13102" "13103" "13104" "13105" "13106"
"13107" "13108" "13109"
"13110" "13111" "13112" "13113" "13114" "13115"
"13116" "13117" "13118"

11. selectInput(
inputId = "pref",
label = " ",
choices = names(choices),
selected = " ",
width = "100%"
)
selectInput(
inputId = "city",
label = " ",
#
choices = choices$` `,
selected = "13112",
width = "100%"
)

12. server <- function(input, output, session) {
observe({
city_choices <- choices[[input$pref]]
city <- input$city
#
#
if (!(city %in% city_choices)) {
city <- city_choices[1]
}
updateSelectInput(
session, inputId = “city",
choices = city_choices, selected = city
)
})
}

16. #
tags$style(type = "text/css", "#map {height: calc(90vh - 80px) !
important;}"),
leafletOutput("map")

17. output$map <- leaflet::renderLeaflet({
leaflet::leaflet() %>%
leaflet::addProviderTiles(providers$CartoDB.Positron)
})

18. observe({
pal <-
leaflet::colorNumeric("Spectral", dat.sub()$n, reverse = TRUE)
map <- leaflet::leafletProxy("map", data = dat.sub()) %>%
leaflet::clearShapes() %>%
leaflet::clearControls() %>%
leaflet::addPolygons(fillColor = ~ pal(n), color = "gray",
popup = ~ NAME, weight = 1,
fillOpacity = 0.8) %>%
leaflet::addLegend("bottomright", pal = pal, values = ~ n,
title = "Population", opacity = 1)
map
})

19. observe({
pal <-
leaflet::colorNumeric("Spectral", dat.sub()$n, reverse = TRUE)
map <- leaflet::leafletProxy("map", data = dat.sub()) %>%
leaflet::clearShapes() %>%
leaflet::clearControls() %>%
leaflet::addPolygons(fillColor = ~ pal(n), color = "gray",
popup = ~ NAME, weight = 1,
fillOpacity = 0.8) %>%
leaflet::addLegend("bottomright", pal = pal, values = ~ n,
title = "Population", opacity = 1)
map
})

23. is.fitBounds <- FALSE
observeEvent(input$city, {
is.fitBounds <<- TRUE
})
observe({
if (is.fitBounds) {
#
bbox <- dat.sub() %>%
sf::st_bbox()
names(bbox) <- NULL
map <- map %>%
leaflet::fitBounds(bbox[1], bbox[2], bbox[3], bbox[4])
is.fitBounds <<- FALSE
}
map

24. is.fitBounds <- FALSE
observeEvent(input$city, {
is.fitBounds <<- TRUE
})
observe({
if (is.fitBounds) {
#
bbox <- dat.sub() %>%
sf::st_bbox()
names(bbox) <- NULL
map <- map %>%
leaflet::fitBounds(bbox[1], bbox[2], bbox[3], bbox[4])
is.fitBounds <<- FALSE
}
map

28. observeEvent(input$map_shape_click, {
p <- input$map_shape_click
#
shp.sub <- shp[[input$pref]] %>%
dplyr::filter(stringr::str_sub(KEY_CODE, 1, 5) %in%
choices[[input$pref]])
#
ind <- sf::st_point(c(p$lng, p$lat), dim = "XY") %>%
sf::st_within(shp.sub) %>% unlist()
})

29. observeEvent(input$map_shape_click, {
p <- input$map_shape_click
#
shp.sub <- shp[[input$pref]] %>%
dplyr::filter(stringr::str_sub(KEY_CODE, 1, 5) %in%
choices[[input$pref]])
#
ind <- sf::st_point(c(p$lng, p$lat), dim = "XY") %>%
sf::st_within(shp.sub) %>% unlist()
})