conditionally output different colored text in Shiny

Question

I would like Shiny to print out some different color text depending on the size of a vector. I was thinking something like:

  output$some_text <- renderText({ 
    if(length(some_vec) < 20){
      paste("This is red text")
      <somehow make it red>
    }else{
    paste("This is blue text")
      <somehow make it blue>

...but then I realized, I'm doing this in the server, not the UI.

And, as far as I know, I can't move this conditional logic into the UI.

For example, something like this won't work in the UI:

    if(length(some_vec)< 20){
         column(6, tags$div(
         HTML(paste("This text is ", tags$span(style="color:red", "red"), sep = ""))
      )}
    else{
         tags$div(HTML(paste("This text is ", tags$span(style="color:blue", "blue"), sep = ""))
)}

Does anyone have any creative ideas?

Answer 1

Inspired by jenesaisquoi's answer I tried the following and it worked for me. It is reactive and requires no additional packages. In particular look at output$text3

library(shiny)

ui <- shinyUI(fluidPage(
  titlePanel("Reactive"),
  sidebarLayout(
    sidebarPanel(
      helpText("Variables!"),
      selectInput("var", 
                  label = "Choose Variable",
                  choices = c("red", "blue",
                              "green", "black"),
                  selected = "Rojo"),
      sliderInput("range", 
                  label = "Range:",
                  min = 0, max = 100, value = c(0, 100))
    ),
    mainPanel(
      textOutput("text1"),
      textOutput("text2"),
      htmlOutput("text3"),
      textOutput("text4")
    )
  )
))

server <- function(input, output) {
  output$text1 <- renderText({ 
    paste("You have selected variable:", input$var)
  })

  output$text2 <- renderText({ 
    paste("You have selected range:", paste(input$range, collapse = "-"))
  })

  output$text3 <- renderText({
    paste('<span style=\"color:', input$var, 
          '\">This is "', input$var, 
          '" written ', input$range[2], 
          ' - ', input$range[1], 
          ' = ', input$range[2] - input$range[1], 
          ' times</span>', sep = "")
  })

  output$text4 <- renderText({ 
    rep(input$var, input$range[2] - input$range[1])
  })
}

# Run the application 
shinyApp(ui = ui, server = server)