CODEWITHSUNDEEP
rshiny
Sungmin Kim
Sungmin Kim

Reputation: 41

Update global variable and return it in R Shiny

I would like to know how to update a global variable by calling a function and return it. Here is my brief code from 'server.R'. My ui.R consists of several lines of code to display the output. 

sentence <- ""
result <- c()

updateSen <- function(input){
   print("function executed!")
   if(length(sentence) == 0){
      result <<- c(result, "First")
      sentence <<- paste(sentence, input, sep = " ")
   }else{
      result <<- c(result, input)
      sentence <<- paste(sentence, input, sep = " ")           
   }
}

shinyServer(
   function(input, output){
      word <- reactive({
         word <- input$tid
      })
      output$oid <- renderText({
         paste(input$tid)
      })

      output$sen <- renderText({
         updateSen(word())
         sentence
      })
   }
)

What I would like to do with the code above is this... 1. Ask user to type a word 2. make a sentence with a word user typed 3. run a function 4. display a sentence

However, it seems like it doesn't work well and there are many things I don't know what's going on. First of all, I have no idea why updateSen() function is called a lot of times during the program execution. Second, the global variable 'result' does not change after the first execution. I would like this variable to be updated.

Upvotes: 1

Views: 2222

Answers (1)

Amanpreet Singh
Amanpreet Singh

Reputation: 45

From what I understand, the variable 'result' will start changing automatically once you apply reactive keyword. Try 

updateSen <- reactive(function(input){
   print("function executed!")
   ...           
   }
})

Secondly, I think you should not have variables like sen and result as 'global' rather you should work with textInput() function and variables like input$sentence. I suggest you read more about reactive variables and functions in Shiny.

Upvotes: 1

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