I'm trying to have thousand separator in my shiny table output.
The following are my code:

```
UI <- dashboardPage(     
  dashboardBody(        
    fluidPage(          
      selectInput(inputId = "TableName",
                  label = "Select Data of Interest",
                  choices = list.files(path = "CSVData", pattern = "AMD_")),          
      uiOutput("Channel"),    
      formattableOutput("ResultTable")         
    )
  )
)

Server <- function(input, output){      
  output$Channel <- renderUI({        
    df <- read.csv(paste("Pathname/",input$TableName, sep = ""))        
    selectInput(inputId = "ChannelSelect",
                label = "Select Channel:",
                choices = unique(df) %>% select(Channel))),
                selected = NULL, multiple = FALSE)        
  })

  output$ResultTable <- renderFormattable({

    df <- read.csv(paste("CSVData/",input$TableName, sep = ""))
    ChanSelect <- input$ChannelSelect    
    A1 <- df %>% filter(if(ChanSelect != "All") (Channel == ChanSelect) else TRUE) %>%
      select(Channel, Amount)        
    formattable(A1, list(
      `Amount` = comma(`Amount`, digits = 0, format = "f", big.mark = ","
    ))        
  })      
}    

```

My df's are varied but all of them are in the format:

```
data.frame("Channel" = c("A", "B", "C", "D"),
           "Amount" = c(1000000, 2000000, 3000000, 4000000 ))

```

The problem is with the formattable part that it didn't work. I don't know how to input the function `comma()` properly with `formattable`.