R Shiny app ggplot2 times out - r

Question

I am building an app to better understand the differences of the lognormal and the normal distribution. The app should display a using ggplot2 a histogram of simulated data (either normal or lognormal) and fit a normal , a lognormal density and a kernel density to the fake data. For some reason the app below wont display the ggplot2 graph.
# Define UI for application that draws a histogram
library(shiny)
library(ggplot2)
library(stats)
library(gridExtra)
set.seed(15)
ui <- fluidPage(
# Application title
titlePanel("Curve fit with different distributions"),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
sliderInput("mean",
"Mean value:",
min = 1,
max = 250,
value = 10)
,
sliderInput("spread",
"Standard deviation:",
min = 0,
max = 25,
step=0.1,
value = 2.5)
,
sliderInput("n",
"How many datapoints:",
min = 10,
max = 10000,
value = 2500)
,
selectInput("dist",
"Which data distribution?" ,
list("Normal"="dnorm" ,
"Lognormal"="dlnorm"
)
)),
# Show a plot of the generated distribution
mainPanel(
plotOutput("distPlot", height = "80%"))
)
)
# Define server logic required to draw a histogram with normal and log normal density
server <- function(input, output) {
sim_data<-reactive({
if(is.null(input$dist) |is.null(input$spread) | is.null(input$mean)) {
return(NULL)
}
mlog<-log(input$mean )
lspread <- log(input$spread)
dat <- data.frame(xn = rnorm(input$n, mean = input$mean, sd = input$spread), ln=rlnorm(input$n, meanlog =mlog , sdlog = lspread))
return(dat)
})
output$distPlot <- renderPlot({
if(is.null(sim_data()) |is.null(input$dist) ){
return(NULL)
}
# generate bins based on input$bins from ui.R
if(input$dist == "dnorm"){
hist_plot<- ggplot(sim_data(), aes(x = xn)) +
geom_histogram(aes(y =..density..),
colour = "black",
fill = "white") +
stat_function(fun = dnorm, colour ="#377EB8", args = list(mean = mymean, sd = mysd))+
stat_function(fun = dlnorm, colour ="#E41A1C", args = list(mean = mylmean, sd = mylsd))+
geom_density(colour="black")+
theme_minimal()
}
else{
hist_plot<- ggplot(sim_data(), aes(x = ln)) +
geom_histogram(aes(y =..density..),
colour = "black",
fill = "white") +
labs(title=distname) +
theme_minimal()+
stat_function(fun = dnorm, colour ="#377EB8", args = list(mean = mymean, sd = mysd))+
stat_function(fun = dlnorm, colour ="#E41A1C", args = list(mean = mylmean, sd = mylsd))+
geom_density(colour="black")+
theme_minimal()
}
if(input$dist == "dnorm"){
box_plot<- ggplot(sim_data(), aes(x="",y = xn)) +
geom_boxplot()+
theme_minimal()
}
else{
box_plot<- ggplot(sim_data(), aes(x="",y = ln)) +
geom_boxplot(
)+
theme_minimal()
}
p=grid.arrange(hist_plot+
theme_minimal(),box_plot+
theme_minimal(), ncol=1,nrow=2, heights = c(4,2))
plot(p)
})
}
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

Hi your problem is here
plotOutput("distPlot", height = "80%")
at the moment you are telling the plot to have the height of 80% of nothing which is nothing. Change the height to 400px for example and it will all work.
Shiny notices that the plot is not visual so it is not even calculating the plot ate the moment.