In jr-packages/jrShiny: R Shiny Exercises

Problem

Suppose we were accessing data from a database, or from a regression model. This means that generating data is time consuming, so we only want to generate the scatter plot when we click the button Plot data, not when we use the sliders.

sliderInput("n", "Sample size", 10, 100, 10)
sliderInput("mean", "Mean", -10, 10, 0)
actionButton("go", "Plot data")

## We only want to plot on "go"
renderPlot(plot(rnorm(input$n, input$mean)))

Solution

Use an actionButton in conjunction with an eventReactive function. This generates a function reactive object that will only be evaluated when the actionButton is pressed.

## input$go is the action button. input$n, input$mean are the sliders
data = eventReactive(input$go, rnorm(input$n, input$mean))
renderPlot(plot(data()))