How to Choose Reactive Argument from a Selective Input?

Question

I have a Select Box Input which changes based on the column names of the loaded .csv file. This is what my observeEvent function does.

I am having trouble when I go to plot the output in server.R, because I am unsure how to craft the reactive argument to transform the output of the SelectizeInput to the column that was chosen from the SelectBox. Does anyone know what I should put inside of the renderDygraph output that will graph the channel that I chose from my SelectizeInput?

Here is my code:

ui.R

shinyUI(fluidPage(

  # Application title
  titlePanel("Graph"),
  fluidRow(
    column(6,
           wellPanel(`

      selectInput("dataSelection1", label = "Choose a File", 
                  choices = c("File1")),
      selectizeInput("channel1", label = "Choose a Channel",
                  choices = NULL))),
     column(12, dygraphOutput("Graph")
            )

      )
    )

  )

server.R

shinyServer(function(input, output, session) {

dataSource1 <- reactive({
    switch(input$dataSelection1,
            "File1" = File1)
        })

observeEvent(input$dataSelection1, { 
    updateSelectizeInput(session, 'channel1', choices = names(dataSource1())) 

})

output$TempRise <- renderDygraph({
        component <- switch(input$channel1,
                            **'WHAT TO PUT IN HERE?'**)
        dygraph(component, main = "Data Graph") %>%
          dyRangeSelector() %>%
          dyOptions(colors = RColorBrewer::brewer.pal(8, "Dark2"))

  })

 })

Answer 1

I don't think you can use a switch statement as you don't know ahead of time what to equate it to, but I do something like this:

shinyServer(function(input, output, session) {

dataSource1 <- reactive({
    switch(input$dataSelection1,
            "File1" = File1)
        })

observeEvent(input$dataSelection1, { 
    updateSelectizeInput(session, 'channel1', choices = names(dataSource1())) 

})

output$TempRise <- renderDygraph({
        data <- dataSource1()
        selected_input <- input$channel1
        component <- data[, selected_input]

        dygraph(component, main = "Data Graph") %>%
          dyRangeSelector() %>%
          dyOptions(colors = RColorBrewer::brewer.pal(8, "Dark2"))

  })

 })