Shiny apps - embedding reactive expression in if-then statement - r

Question

I'm having difficult using reactive expression in Shiny Apps. I'm creating a pie chart from slider input. This all works fine, however, the labels overlap. To avoid this I would like the label "" when the input is zero. The difficulty is that I'm unable to embed a reactive expression within an if-then statement.
Here is an MWE...
File "ui.R"...
library(shiny)
shinyUI(fluidPage(
titlePanel("Exposure to English calculator"),
sidebarLayout(
sidebarPanel(
h3("Sleeping"),
sliderInput("sleep", "How long does your child sleep every day?",
min=0, max=15, value=0, step = 0.5),
h3("School"),
sliderInput("school", "How long does your child spend in school?",
min = 0, max = 50, value=0, step = 0.5)
),
mainPanel(
plotOutput("plot")
)
)
))
File server.R...
library(shiny)
values <- c(1,2)
# Define server logic for slider examples
shinyServer(function(input, output) {
total_sleep <- reactive({7*input$sleep})
pieLabels<-c("sleep", "school", "other")
if(total_sleep() == 0) {
pieLabels[1] <- ""
}
output$plot <- renderPlot({
pie(c(total_sleep(), input$school, 50),
labels = pieLabels,
col = c("deepskyblue", "orange"),
height = 1500
)
})
})
The compilation crashes due to the "if" expression even though I've put the brackets after it, to show that it is derived from a reactive expression.
Thanks in advance.

Answer 1

You can just put all your total_sleep code and conditional statement inside the renderPlot function:
library(shiny)
app <- shinyApp(
ui = shinyUI(fluidPage(
titlePanel("Exposure to English calculator"),
sidebarLayout(
sidebarPanel(
h3("Sleeping"),
sliderInput("sleep", "How long does your child sleep every day?",
min=0, max=15, value=0, step = 0.5),
h3("School"),
sliderInput("school", "How long does your child spend in school?",
min = 0, max = 50, value=0, step = 0.5)
),
mainPanel(
plotOutput("plot")
)
)
)),
server = shinyServer(function(input, output) {
output$plot <- renderPlot({
total_sleep <- 7*input$sleep
pieLabels<-c("sleep", "school", "other")
if(total_sleep == 0) {
pieLabels[1] <- ""
}
pie(c(total_sleep, input$school, 50),
labels = pieLabels,
col = c("deepskyblue", "orange")
)
})
}))
runApp(app)
Note that I removed the height from pie because that argument doesn't exist and that gives out a warning.