text_eval_shiny_example.R

library(shiny)
library(lazyeval)

ui <- fluidPage(
   titlePanel("text eval"),
   
   sidebarLayout(
      sidebarPanel(
         textInput("text",
                     "formula:",
                     value = "")
      ),
      
      mainPanel(
         textOutput("result")
      )
   )
)

server <- function(input, output) {
  
  formula <- reactive({
      ifelse(input$text != "", 
             lazyeval::lazy_eval(input$text),
             "no text input"
             )
    })
   
   output$result <- renderText({
     formula()
   })
}

shinyApp(ui = ui, server = server)