Source vs. Conductor vs. Endpoint
The magic behind Shiny is driven by reactivity. As you learned in this lesson, there are three types of reactive components in a Shiny app.
- Reactive source: User input that comes through a browser interface, typically.
- Reactive conductor: Reactive component between a source and an endpoint, typically used to encapsulate slow computations.
- Reactive endpoint: Something that appears in the user's browser window, such as a plot or a table of values.
ui <- fluidPage(
titlePanel('BMI Calculator'),
theme = shinythemes::shinytheme('cosmo'),
sidebarLayout(
sidebarPanel(
numericInput('height', 'Enter your height in meters', 1.5, 1, 2),
numericInput('weight', 'Enter your weight in Kilograms', 60, 45, 120)
),
mainPanel(
textOutput("bmi"),
textOutput("bmi_range")
)
)
)
server <- function(input, output, session) {
rval_bmi <- reactive({
input$weight/(input$height^2)
})
output$bmi <- renderText({
bmi <- rval_bmi()
paste("Your BMI is", round(bmi, 1))
})
output$bmi_range <- renderText({
bmi <- rval_bmi()
health_status <- cut(bmi,
breaks = c(0, 18.5, 24.9, 29.9, 40),
labels = c('underweight', 'healthy', 'overweight', 'obese')
)
paste("You are", health_status)
})
}
shinyApp(ui, server)
In this exercise, you will be presented with a set of reactive components. Classify each as a reactive source, conductor, or endpoint.
This exercise is part of the course
Building Web Applications with Shiny in R
Hands-on interactive exercise
Turn theory into action with one of our interactive exercises
