R 将字符串连接到输入变量中

我正在尝试构建Shinny应用程序，它将使用quantmod软件包根据输入要求下载和绘制股票数据。在Shinny中，输入作为ex:TCS的股票名称。然而，quantmod采用的股票符号是TCS.NS

ui <-fluidPage(
    titlePanel("Stock Analysis"),
    sidebarLayout(
        sidebarPanel(
            selectInput(inputId = "symbols",label="Enter Stock Name",
                        choices="TCS","MARUTI","HDFCBANK"),
            dateInput("start_date",h3("start Date"),value="2019-01-01"),
            dateInput("end_date",h3("End Date"),value="2019-09-01"),
......

ui这行

input$symbols <-paste0(input$symbols,".NS",sep="")

Warning: Error in $<-.reactivevalues: Attempted to assign value to a read-only reactivevalues object

input$symbols <-paste0(input$symbols,".NS",sep="")

newObj <-paste0(input$symbols,".NS")
data <- getSymbols(newObj,from=input$start_date,to=input$end_date,auto.assign=FALSE)