apps/CycleHireApp/app.R

In Robinlovelace/geocompr: Geocomputation with R

# Shiny app for cycle hire from https://github.com/geocompx/geocompr/issues/584
# Author - Kiranmayi Vadlamudi
# 2020-12-25
# Last updated: 2023-04-19 by Jakub Nowosad
library(shiny)
library(sf)
library(spData)
library(spDataLarge)
library(leaflet)
library(units)
library(dplyr)
library(stringr)

# Based on input coordinates finding the nearest bicycle points
ui = fluidPage(
  # Application title
  titlePanel("CycleHireApp"),
  # Numeric Input from User
  bootstrapPage(
    div(style = "display:inline-block", 
        numericInput("x", ("Enter x-coordinate of your location"), value = 51.5, step = 0.001)),
    div(style = "display:inline-block", 
        numericInput("y", ("Enter y-coordinate of your location"), value = -0.1, step = 0.001)),
    div(style = "display:inline-block", 
        numericInput("num", "How many cycles are you looking for?", value = 1, step = 1))
    ),
  # Where leaflet map will be rendered
  fluidRow(
    leafletOutput("map", height = 300)
  )
)

server = function(input, output) {
  #Centering the leaflet map onto London - use if needed
  map_centre = matrix(c(-0.2574846, 51.4948089), nrow = 1, ncol = 2, 
                      dimnames = list(c("r1"), c("X", "Y")))
  
  #Based on input coords calculating top 5 closest stations to be displayed 
  
  #Making reactive object of input location coordinates
  input_pt = reactive({
    matrix(c(input$y, input$x), nrow = 1, ncol = 2,
           dimnames = list(c("r1"), c("X", "Y")))
  })
  #Rendering the output map showing the input coordinates
  output$map = renderLeaflet({
    leaflet() |> 
      addTiles() |>
      setView(lng = input_pt()[, "X"], input_pt()[, "Y"], zoom = 15)
  })
  #Finding the top distance between input coordinates and all other cycle stations, then sorting them.
  data = reactive({
    cycle_hire$dist = st_point(input_pt()) |>  
      st_sfc() |> 
      st_set_crs("EPSG:4326") |> 
      st_distance(cycle_hire$geometry) |>
      t() |> 
      set_units("km")
    
    cycle_hire[order(cycle_hire$dist), ]
  })
  #Filtering the distance data from above to show top 5 closest stations meeting requirement of # of bikes needed  
  filteredData = reactive({
    data() |> 
      filter(nbikes >= input$num) |> 
      head(5) |> 
      mutate(popup = str_c(str_c("Station:", name, sep = " "),
                     str_c("Available bikes:", nbikes, sep = " "), sep = "<br/>"))
    
  })
  #Making changes to the output leaflet map reflecting the cycle stations found above
  icons = awesomeIcons(icon = "bicycle", library = "fa",
                       squareMarker = TRUE, markerColor = "blue")
  
  observe({
    proxy = leafletProxy("map", data = filteredData()) |> clearMarkers()
    
    proxy |>
      clearMarkers() |> 
      addAwesomeMarkers(icon = icons, popup = ~popup) |> 
      addMarkers(lng = input_pt()[, "X"], input_pt()[, "Y"], label = "Your Location")
    
  })
}
# Run the application
shinyApp(ui = ui, server = server)