In jr-packages/jrShiny: R Shiny Exercises

Problem

We have two action buttons. When we click a button, we wish to generate a new plot. However, dependencies within reactive function are constructed dynamically as the code is run. In the case below, because input$unif is not executed, then it is not included as a dependency.

actionButton("norm", "Normal")
actionButton("unif", "Uniform")
## Reactive dependencies are dynamic
rv1 = reactive({
  if(input$norm) {
    rnorm(100)
  } else if(input$unif){
    runif(100)
  } else {
    rnorm(100)
  }
})

renderPlot(plot(rv1()))

Solution

Combine reactiveValues and observeEvents. * reactiveValues creates a list of reactive values that you can update in your code * You can update the reactive values from inside a call to

rv2 = reactiveValues(data = rnorm(100))

observeEvent(input$norm, {rv2$data = rnorm(100)})
observeEvent(input$unif, {rv2$data = runif(100)})
renderPlot({plot(rv2$data)})

Further information

• https://shinydata.wordpress.com/2015/02/02/a-few-things-i-learned-about-shiny-and-reactive-programming/

jr-packages/jrShiny documentation built on Feb. 16, 2020, 9:13 p.m.