R Shiny create input using renderUI and function results

Question

I am new to R Shiny and I am trying to create an app which I need it to be as interactive as possible. One problem that I am dealing with is this. In the ui.R I have the following:

helpText("Select a feature"),
uiOutput("sliders")

And in the server.R:

output$sliders <- renderUI({
    selectInput('feature_name', 
                'Feature name', #Description  
                choice = c("F1"='1', "F2"='2'))
  })

My question is that is it possible to change something in renderUI so that instead of setting c("F1"='1', "F2"='2')) statically I can pass the results of a function to it so it can be more dynamic (a function which generates a feature list based on something that user does and passes the list to renderUI to create the selectInput). Something like following:

output$sliders <- renderUI({
    selectInput('feature_name', 
                'Feature name', #Description  
                choice = c(feature_creator(method)))
  })

Where "feature_creator" is a function and it returns: "F1"='1', "F2"='2' based on the method selected by user (variable "method" is defined and I have the value). My question to be more specific is what should "feature_creator" return as output?

Hope my question is clear enough. Let me know if I should add anything to the problem description.

Any help will be much appreciated. Thanks

Short answer - yes you can do that, but without a more specific question it is hard to give a real answer. — John Paul
– John Paul, Commented Jul 22, 2015 at 18:57

John Paul · Accepted Answer · 2015-07-22 19:46:07Z

1

Assuming that all you really need is the method argument, this is not hard.

1) Make a radioButtons() input in your ui that will let the user select a method, lets give it inputId="MethodChoice".

2) In your choice argument in the selectInput you should use choice=c(feature_creator(input$MethodChoice))

Then feature_creator will get a text value based on the method the user chooses.

In order to work in choice, feature_creator should return a named list, similar in format to what you hard-coded.

edited Jul 22, 2015 at 19:46

answered Jul 22, 2015 at 19:21

John Paul

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2 Comments

ahajib Over a year ago

John I edited my question again. The method is defined and the thing that I can not figure out is: what should feature_creator return so it looks like : "F1"='1', "F2"='2'. I have already tried returning it as a string which I am sure is incorrect and it is not working.

ahajib Over a year ago

Awesome. Named list, thats what I have been looking for all day. Thanks John

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