How to use variables in a switch statement?

Question

I have about 50 files that I need to call within dataSource1, dataSource2, and dataSource3. Instead of copying it all out into each switch statement, how can I use variables so I only have to type it out once at the top of the code? I am calling this within server.R for a Shiny App.

dataSource1 <- reactive({
        switch(input$dataSelection1,
               "File1" = File1,
               "File2" = File2,
               "File3" = File3,
               "File50" = File50
)
        )

Instead, I would like to have:

dataSource1 <- reactive({
            switch(input$dataSelection1,
                   FileNumber = File
                   )
        )
dataSource2 <- reactive({
            switch(input$dataSelection1,
                   FileNumber = File
                   )
        )
dataSource2 <- reactive({
            switch(input$dataSelection1,
                   FileNumber = File
                   )
        )

Answer 1

You can use the get function that will return the value of a named object. Assuming that input$dataSelection1 has the complete name of the variable, your reactive function could be something like this:

 dataSource1 <- reactive({
            get(input$dataSelection1)
        )

It will return the content of the variable that match the name.

If input$dataSelection1 only contains a number, you can use the paste0 or sprintf functions to build the name of the variable:

get(paste0('File',input$dataSelection1)) # it will create File1, File2...
sprintf('File%04d',input$dataSelection1) # add zeros before the number File0001

I hope it can help you.