Change data on leaflet plot based on inputted date (R, Shiny)

Question

I am attempting to create a Shiny app using R that plots coordinate data on a map via leaflet. The data also has date stamps, and I want to be able to plot a specific days' coordinates as chosen by the user. I'm brand new to both R and Shiny so all help is appreciated. Here is a snippet of the dataframe;

 Date    |   InitialLat | InitialLong |    NewLat   |  NewLong  |
13/05/16 |   53.477403  | -2.230932   |  51.527953  | -0.13216  |
13/05/16 |   53.490599  | -2.312568   |  53.485655  | -2.237405 |
14/05/16 |   53.371535  | -2.23148    |  53.32803   | -2.246991 |
14/05/16 |   53.371535  | -2.23148    |  53.32803   | -2.246991 |
15/05/16 |   53.371535  | -2.23148    |  53.32803   | -2.246991 |
15/05/16 |   53.371535  | -2.23148    |  53.32803   | -2.246991 |
16/05/16 |   53.478316  | -2.23270    |  53.42814   | -2.17458  |
16/05/16 |   53.48868   | -2.21839    |  53.47737   | -2.23091  |

My code so far:

library(shiny)
library(leaflet)

cleanData <- read.csv(file="CleanedJourneyData.csv", header=TRUE, sep=",")
cleanData$X <- NULL

ui <- fluidPage(
  dateInput(inputId = "n_date", label="Select a date", value = "2016-05-13", min = "2016-05-13", max = "2016-10-24",
            format = "dd-mm-yyyy", startview = "month",
            language = "en", width = NULL),
  leafletOutput("map")

)

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

  dailyData <- reactive(cleanData[cleanData$Date == format(input$n_date, '%d/%m/%y')] )

  output$map <- renderLeaflet({  leaflet(dailyData) %>% addTiles() %>% 
      addMarkers(~InitialLong, ~InitialLat, popup = "Start")  })
}

shinyApp(ui, server)

The problem lies in the line;

dailyData <- reactive(cleanData[cleanData$Date == format(input$n_date, '%d/%m/%y')] )

The error I get is:

Error: no applicable method for 'doResolveFormula' applied to an object of class "reactive"

What I'm trying to achieve is;

the user selects a date
the format of the date is changed to '%d/%m/%y'
the inputted date is then used to search the dataframe (cleanData) to create a new dataframe (dailyData) of just the lat/long coordinates from that selected date
the trimmed down dataframe is inputted into the leaflet map and displayed

The date input works fine, I can get the date in the right format, but when I try and use this to search cleanData to create the dailyData it doesn't work, and I cannot figure it out. What am I doing wrong? For the record I was able to get this to work outside of Shiny - I manually changed the date in the code and the corresponding coordinates were plotted through the leaflet.

there is an error in your reactive function. It should be reactive({})..curly braces are missing — MLavoie
A reactive is a function that returns data, not data itself. To get the data, call it like this leaflet(dailyData()) — HubertL

SBista SBista · Accepted Answer · 2017-02-02T12:27:22

I have modified your code. Just have a look if this is what you really want.

library(shiny)
library(leaflet)

cleanData <- read.csv(file="D:/CleanedJourneyData.csv", header=TRUE, sep=",")
cleanData$X <- NULL

ui <- fluidPage(
  dateInput(inputId = "n_date", label="Select a date", value = "2016-05-13", min = "2016-05-13", max = "2016-10-24",
            format = "dd-mm-yyyy", startview = "month",
            language = "en", width = NULL),
  leafletOutput("map")

)

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

  dailyData <- reactive(cleanData[cleanData$Date == format(input$n_date, '%d/%m/%y'), ] )

  # I have implemented the change here, instead of using dailyData, I've used isolate(dailyData())
  output$map <- renderLeaflet({ leaflet(isolate(dailyData())) %>% addTiles() %>% 
                                   addMarkers(~InitialLong, ~InitialLat, popup = "Start")  })

}

shinyApp(ui, server)

Hope it helps!

Change data on leaflet plot based on inputted date (R, Shiny)

2 Answers