在闪亮的应用程序的selectinput小部件中包含选项NULL

Question

I'm running into some issues in my work. To iullustrate the problem, I'm using the diamonds data as an example.

I made a function sca.plot. If the argument color.by=NULL, then make a scatter plot and color all points red. If color.by is some factor variable, make scatter plot and color points by the variable.

My question is when I make interactive scatter plot in shiny. How can I include the NULL option in selectinput widget, so that I can choose whether or not those points are colored by some variable?

If I include NULL in choices in selectinput, I got errors. Could not figure it out....

Thanks a lot in advance.

Below is my code:

library(ggplot2)

sca.plot <- function (color.by=NULL) {
    if (is.null(color.by)) {
        diamonds %>% ggplot(aes(x, y))+
            geom_point (color='red')
    } else {
        color.by = sym(color.by)
        diamonds %>% ggplot(aes_(~x, ~y, color=color.by))+
            geom_point ()
    }
}

sca.plot(color.by='clarity')

ui <- fluidPage(
    sidebarLayout(
        sidebarPanel(
            selectInput('colorby', label = h5(strong('Color By')),
                        choices = list('clarity', 'cut'),
                        selected = NULL)
        ),
        mainPanel(
            plotOutput('plot') 
            )
        )
    )


server <- function(input, output) {

    output$plot <- renderPlot ({
        sca.plot(color.by=input$colorby)
    })
}

runApp(shinyApp(ui, server))

Answer 1

Here is the solution for you:

library(ggplot2)
library(shiny)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      selectInput('colorby', label = h5(strong('Color By')),
                  choices = list('NULL','clarity', 'cut'),
                  selected = NULL)
    ),
    mainPanel(
      plotOutput('plot') 
    )
  )
)


server <- function(input, output) {

  output$plot <- renderPlot ({
    if(!input$colorby == 'NULL'){
    ggplot(diamonds, aes_string(x="x",y="y", color=input$colorby)) +
        geom_point()
      }else{
      ggplot(diamonds, aes(x=x,y=y)) +
        geom_point(color='red')
    }
  })
}
shinyApp(ui = ui, server = server)

You can use NULL as an argument in selectInput but as a string --> 'NULL'

You actually do not need such a function as you wrote at the beginning of shiny app, you can easily use if...else... statement directly in renderPlot() to get the desired color of the geom_point() .