How to make a for loop reactive in shiny server?

[umair durrani]

I am using assign in for loop to create new variables that I want to use in more than one outputs in shiny ui. Following is a sample code:

library(shiny)
ui <- fluidPage(

  mainPanel(fluidRow(textOutput("a")),
            fluidRow(textOutput("b")))
)
server <- function(input, output) {

  m <- reactive({1:5})

  output$a <- renderPrint({

    for (i in 1:length(m())){
      assign(paste0("h",i), "u")
      }

    list(h1,h2)
  })

  output$b <- renderPrint({

   list(h1,h2)
  })
}
shinyApp(ui = ui, server = server)

How can I make for loop reactive and put it outside `output` function so that all `output` functions could access the h variables?

Note: question posted on stackoverflow as well.

[David Zornek]

If you mean, make the code react to a user input for number of variables, then all you need to do is create an input widget for the user to select the number of variables. Either a sliderInput or numericInput or selectInput will do.

Then, you won't need m <- reactive({1:5}). You can just have your loop reference the input like this: for(i in 1:input$number){ your code }.

As for making the variables accessible by other functions, you should be able to use the envir argument of assign() to scope it to a different environment that's more accessible. Try envir = globalnenv().

[Joe Cheng]

When h1/h2 change, do you want output$b to update? If so, these are not normal variables but reactive values.

server <- function(input, output) {

  m <- reactive({1:5})

  v <- reactiveValues()

  output$a <- renderPrint({

    for (i in 1:length(m())){

      v[[paste0("h",i)]] <- "u"

    }

    list(v$h1,v$h2)

  })

  output$b <- renderPrint({

   list(v$h1,v$h2)

  })

}

shinyApp(ui = ui, server = server)

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