Force no default selection in selectInput()

Question

The Shiny documentation mentions that for selectInput():

selected The value (or, if none was supplied, the title) of the naviga

Answer 1

@Yihui Xie's answer requires selectInput(..., selectize = TRUE). If you want selectize = FALSE, you can still achieve a similar effect as follows.

This is not documented:

selected The initially selected value (or multiple values if multiple = TRUE). If not specified then defaults to the first value for single-select lists and no values for multiple select lists.

But for single-select lists if you can use selectize = FALSE, size = 4 (any non-NULL size would work), then you can set selected = FALSE to force no default selection.

library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(
      mainPanel(
         uiOutput("Choose_Molecule")
      )
)

# Define server logic required to draw a histogram
server <- function(input, output) {

    # First UI input (Service column) filter clientData 
    output$Choose_Molecule <- renderUI({
        selectInput("molecule",
                    "Select Molecule:",
                    choices = rownames(mtcars),
                    selected = FALSE,
                    multiple = FALSE
                    , selectize = FALSE, size = 4  ##needed for `selected = FALSE` to work
        )
    })

}

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