How can I not to select any option in radioButtons?
From this doc:
selected The initially selected value (if not specified then defaults
to the first value)
From the Documentation:
If you need to represent a "None selected" state, it's possible to default the radio buttons to have no options selected by using selected = character(0). However, this is not recommended, as it gives the user no way to return to that state once they've made a selection. Instead, consider having the first of your choices be c("None selected" = "").
Hope this helps.