Using dygraph with shiny

I recently started using dygraph and I quite enjoyed it so far. I have tried to use it then with shiny without much success. Although my script doesn't yield any errors, it also doesn't produce any graph!
Any chance you could guide me in the right direction?

here is a sample of my data:

> head(df2)
        date     Variety   Count Price Value Quantity TotalKg
1 2014-11-06 CRIPPS PINK   80-90   204  3670       18     333
2 2014-11-06 CRIPPS PINK 120-135   181 10150       56    1036
3 2014-11-06  CRIPPS RED   80-90   221 26910      122    2257
4 2014-11-06  CRIPPS RED 100-110   205 22910      112    2072
5 2014-11-06  CRIPPS RED 120-135   193 58950      306    5661
6 2014-11-06      TOPRED   80-90   167  7350       44     814

Using the Variety and Count variables, I would like to graph the price over time.

Here is my ui.R

library(dygraphs)
library(shiny)

shinyUI(fluidPage(
  titlePanel("Apples Prices"),
  
  sidebarLayout(
          sidebarPanel(
            selectInput("productname", "Select your product",
                        choices = levels(df2$Variety)),
            selectInput("count",  "Select your size",
                        choices = levels(df2$Count))),
                                         
            mainPanel(
              dygraphOutput("applesgraph"))
          )))

and the server side:

library(shiny)
library(dygraphs)
library(dplyr)
library(xts)

shinyServer(function(input, output) {

  dfa <- reactive({df2 %>% filter(Variety == input$productname & 
                                    Count == input$count )})
  
#the first graph which is price over time (input: variety, count, date)
  output$applesgraph <- renderDygraph({
   xts(dfa()$Price, order.by = dfa()$date) %>% dygraph()
  })
})

I can feel I am having the wrong approach with dplyr and time series object ... when should I filter then? I have tried many combination, but then I have always errors such as "not subsetable".

Since you need the input data in server.R (for the graph) and in ui.R (for the input list), I added a renderUI({...}) in server.R and an uiOutput(...) in ui.R

# server.R
library(shiny)
library(dygraphs)
library(dplyr)
library(xts)

shinyServer(function(input, output) {
  data <- read.csv("cleanApples.csv") %>%
    filter(Quantity > 10)

  #the first graph which is price over time (input: variety, count, date)
  output$applesgraph <- renderDygraph({
    if (is.null(input$productname) || is.null(input$count)) return(NULL)
    filtered <- filter(data,
                       Variety == input$productname,
                       Count == input$count )
    xts(filtered$Price, as.Date(filtered$date, format = "%Y-%m-%d")) %>%
      dygraph()
  })

  output$productnames <- renderUI({
    selectInput("productname", "Select your product",
                choices = levels(data$Variety))
  })

  output$counts <- renderUI({
    selectInput("count",  "Select your size",
                choices = levels(data$Count))
  })
})

And

# ui.R
library(dygraphs)
library(shiny)

shinyUI(fluidPage(
  titlePanel("Apples Prices"),

  sidebarLayout(
    sidebarPanel(
      uiOutput("productnames"),
      uiOutput("counts")
    ),

    mainPanel(
      dygraphOutput("applesgraph"))
  )))

Now it works in shinyapps.io