can we have loop in ui.R

[tanthiamhuat]

I understand we can write loop in server.R, but are we able to have loop in ui.R?

My need for loop in ui.R is this:
say if user selects certain input from pull-down menu with value=1, I want the width of my dygraph to be 12, otherwise with pull-down menu with value=0, I want the width of my dygraph to be 6.

If loop is not able to be achieved in ui.R, how can I achieve the above?

[andresrcs]

To help us help you, could you please prepare a reproducible example (reprex) illustrating your issue? Please have a look at this guide, to see how to create one for a shiny app

Shiny debugging and reprex guide

Shiny issues can be challenging to resolve relative to other problems with your code or statistical methods. Shiny apps are often large, complex projects with interacting files. When seeking help from others it is considered polite to: First, do your best to work through RStudio's debugging tools to diagnose your issue on your own. Often those shiny logs and tracebacks are useful to others trying to help out. Second, strive to minimize the effort required to replicate your issue. You can do this with a reproducible example ("reprex"). Shiny Debugging Errors in Shiny code can be difficult to track down. If you don't know where your problem is coming from, you can track it down with some o…

[Danieldavid521]

highly suggest you read Mastering_Shiny this is what reactivity is all about

[nirgrahamuk]

A rule of thumb for you is that ui.R is to position static UI elements. If you need dynamic parts, then you place containers for them with uiOutput and then give them renderUI definitions in your server code

[tanthiamhuat]

do you have an example?

[Danieldavid521]

shinyApp(
  ui = fluidPage(
    selectInput("state", "Choose a state:",
      list(`East Coast` = list("NY", "NJ", "CT"),
           `West Coast` = list("WA", "OR", "CA"),
           `Midwest` = list("MN", "WI", "IA"))
    ),
    textOutput("result")
  ),
  server = function(input, output) {
    output$result <- renderText({
      paste("You chose", input$state)
    })
  }
)
}

in Shiny, it's not IF a user selects a value, it's coded for WHEN a user selects input. In normal coding you think linearly, but in Shiny, code is only ran WHEN it is needed

[nirgrahamuk]

https://shiny.rstudio.com/gallery/dynamic-ui.html