In Shiny apps (or R markdown): colourInput()

You can use colourInput() to include a colour picker input in Shiny apps (or in R markdown documents). It works just like any other native Shiny input, here is an example:

library(shiny)
shinyApp(
    ui = fluidPage(
        colourInput("col", "Select colour", "purple"),
        plotOutput("plot")
    ),
    server = function(input, output) {
        output$plot <- renderPlot({
            set.seed(1)
            plot(rnorm(50), bg = input$col, col = input$col, pch = 21)
        })
    }
)

Demo of colourInput

To select colours to use in your R code: colourPicker()

colourpicker also provides an RStudio addin that can be used to easily select colours and save them as a variable in R. This can be useful if, for example, you want to pick some colours for a plot and you want an easy way to visualize and select a few colours. Here is a screenshot of the colour picker addin (you can either access this tool using the Addins menu or with colourPicker()). You can also watch a short GIF of it an action.

Demo of colour picker addin

As an ‘htmlwidgets’ widget

The colour picker input is also available as an ‘htmlwidgets’ widget using the colourWidget() function. This may not be terribly useful right now since you can use the more powerful colourInput in Shiny apps and Rmarkdown documents, but it may come in handy if you need a widget.

Simple and familiar

Using colourInput is extremely trivial if you’ve used Shiny, and it’s as easy to use as any other input control. It was implemented to very closely mimic all other Shiny inputs so that using it will feel very familiar. You can add a simple colour input to your Shiny app with colourInput("col", "Select colour", value = "red"). The return value from a colourInput is an uppercase HEX colour, so in the previous example the value of input$col would be #FF0000 (#FF0000 is the HEX value of the colour red). The default value at initialization is white (#FFFFFF).

Allowing “transparent”

Since most functions in R that accept colours can also accept the value “transparent”, colourInput has an option to allow selecting the “transparent” colour. By default, only real colours can be selected, so you need to use the allowTransparent = TRUE parameter. When this feature is turned on, a checkbox appears inside the input box.

If the user checks the checkbox for “transparent”, then the colour input is grayed out and the returned value of the input is transparent. This is the only case when the value returned from a colourInput is not a HEX value. When the checkbox is unchecked, the value of the input will be the last selected colour prior to selecting “transparent”.

By default, the text of the checkbox reads “Transparent”, but you can change that with the transparentText parameter. For example, it might be more clear to a user to use the word “None” instead of “Transparent”. Note that even if you change the checkbox text, the return value will still be transparent since that’s the actual colour name in R.

This is what a colour input with transparency enabled looks like

allowTransparent demo

How the chosen colour is shown inside the input

By default, the colour input’s background will match the selected colour and the text inside the input field will be the colour’s HEX value. If that’s too much for you, you can customize the input with the showColour parameter to either only show the text or only show the background colour.

Here is what a colour input with each of the possible values for showColour looks like

showColour demo

Updating a colourInput

As with all other Shiny inputs, colourInput can be updated with the updateColourInput function. Any parameter that can be used in colourInput can be used in updateColourInput. This means that you can start with a basic colour input such as colourInput("col", "Select colour") and completely redesign it with

updateColourInput(session, "col", label = "COLOUR:", value = "orange",
  showColour = "background", allowTransparent = TRUE, transparentText = "None")

Limited colour selection

This feature is available in shinyjs v0.0.8.0, which is currently only on GitHub and not on CRAN.

If you want to only allow the user to select a colour from a specific list of colours, rather than any possible HEX colour, you can use the palette = "limited" parameter. By default, the limited palette will contain 40 common colours, but you can supply your own list of colours using the allowedCols parameter. Here is an image of the default limited colour palette.

colourInput demo

Flexible colour specification

Specifying a colour to the colour input is made very flexible to allow for easier use. When giving a colour as the value parameter of either colourInput or updateColourInput, there are a few ways to specify a colour:

• Using a name of an R colour, such as red, gold, blue3, or any other name that R supports (for a full list of R colours, type colours())
• If transparency is allowed in the colourInput, the value transparent (lowercase) can be used. This will update the UI to check the checkbox.
• Using a 6-character HEX value, either with or without the leading #. For example, initializing a colourInput with any of the following values will all result in the colour red: ff0000, FF0000, #ff0000.
• Using a 3-character HEX value, either with or without the leading #. These values will be converted to full HEX values by automatically doubling every character. For example, all the following values would result in the same colour: 1ac, #1Ac, 11aacc.

Works on any device

If you’re worried that maybe someone viewing your Shiny app on a phone won’t be able to use this input properly - don’t you worry. I haven’t quite checked every single device out there, but I did spend extra time making sure the colour selection JavaScript works in most devices I could think of. colourInput will work fine in Shiny apps that are viewed on Android cell phones, iPhones, iPads, and even Internet Explorer 8+.