Shiny selectInput interactive controls in R

Symbol of coding on a computer screen

selectInput() syntax

selectInput(inputId, label, choices, selected = NULL, multiple = FALSE, selectize = TRUE, width = NULL, size = NULL)

The control creates a dropdown list, but the ‘size‘ argument can be used to set the control in a selection box.

  • inputID – unique name for the control, not displayed to the user;
  • label – text label for the input placed above the dropdown, visible to the user;
  • choices – the text items that the user can select from;
  • selected – NULL/string; whether there is already an item pre-selected in the dropdown field;
  • multiple – TRUE/FALSE; can the user select more than one item from the dropdown;
  • selectize – TRUE/FALSE; whether to enable selective.js in the control;
  • width – width of the input control, in px or as a %;
  • size – the number of items to show in a selection box, the larger the number the taller the box. (Not compatible with selectize=TRUE.)
  • ... – additional arguments, and selective.js options can also be included.

Add R Shiny interactive selectInput selection controls

A selectInput() control can be placed on its own in a layout:


… or within a ‘panel’, e.g. inside an inputPanel() layout (as shown in the document default content above). This will place the input inside a formatted panel.

                        choices =c("Red","Green","Blue"))

The selectInput choices list

The list of choices in the selectInput control can be fed from different sources:

  • a list within the function: choices=c("A","B","C")
  • a list variable defined outside of the function:
choices_list <- c("A","B","C")
  • a subset of a matrix/data table, e.g. the user first selects a category, and the list of choices is taken from that category (where table=datatable, input$category is the output from the user selectInput ID ‘category’, and items are the items within the chosen category).
            choices = unique(subset(datatable, category==input$category, 

External link icon See more on how to create a selectInput dependent on another Shiny input control

>> On the next page we show how to use the output from a selectInput() function

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