Why does my plot disappear in shiny when I add a table? - r

Question

I have created a shiny app should take input from three sliders and:
Plots a distribution in ggplot
Show a summary table of values underneath the plot in #1 above
If I just want to plot the histogram (and I comment out the table data), I can get the code to work correctly. However, when I add the table, the plot disappears even though the plot header is still there. I have tried moving the commas a braces around to see if it's a simple syntax error but haven't had any luck.
library(shiny)
# Define UI for application that draws a histogram
shinyUI(fluidPage(
# Application title
titlePanel("Test Shiny Layout"),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
h4("Input Data"),
sliderInput("bins", "Bin Width", min = 4,max = 12, value = 8),
),
# Show a plot of the generated distribution
mainPanel(
h4("Histogram"),
plotOutput("distPlot", width = "600", height = "600"),
h4("Table of Values"),
tableOutput("table")
)
)
))
Server
library(shiny)
library(ggplot2)
# Define server logic required to draw a histogram
shinyServer(function(input, output) {
output$distPlot <- renderPlot({
bins <- input$bins
df1 <- (iris$Sepal.Length)
x <- mean(df1)
y <- sd(df1)
ggplot(data = iris) +
geom_histogram(mapping = aes(x = Sepal.Length), color = "blue", binwidth = "bins")
# Create an empty dataframe and then plug in the mean and standard deviation
results <- data.frame("0", "0")
results[1,1] = x
results[1,2] = y
colnames(results) <- c("Mean", "SD")
rownames(results) <- c("Sepal Length")
output$table <- renderTable(results)
})
})

Answer 1

Your renderTable() is inside your renderPlot() call. So renderPlot isn't returning anything.
You were right: it was a simple syntax error. But you also had several other issues in your code. At least a dozen. Three in binwidth = "bins" alone.
Here's a working version. I suspect you will still want to make tweaks, but at least you have both a histogram and a summary table that both look reasonably sensible.
library(shiny)
library(ggplot2)
data(iris)
# Define server logic required to draw a histogram
server <- function(input, output) {
output$distPlot <- renderPlot({
ggplot(data = iris) +
geom_histogram(aes(x = Sepal.Length), color = "blue", bins = input$bins)
})
output$table <- renderTable({
iris %>%
summarise(Mean=mean(Sepal.Length),
SD=sd(Sepal.Length))
})
}
ui <- fluidPage(
titlePanel("Test Shiny Layout"),
sidebarLayout(
sidebarPanel(
h4("Input Data"),
sliderInput("bins", "Bin Width", min = 4,max = 12, value = 8),
),
mainPanel(
h4("Histogram"),
plotOutput("distPlot", width = "600", height = "600"),
h4("Table of Values"),
tableOutput("table")
)
)
)
shinyApp(ui = ui, server = server)