Update Graph in R Shiny react - r

Question

I would like to understand why the graph does not update in the RShiny App generated from the code below.
What I try to do:
Generate a sample of n_data observations from a beta-distribution with certain shape parameters.
Plot the histogram of this sample, together with its mean.
Do this e_samples times and keep the means, show an updated graph every second
Plot the histogram of the vector with e_samples means
library(shiny)
library(ggplot2)
# Design the interface
ui <- fluidPage(titlePanel("Population vs sample"),
sidebarLayout(
# Function to determine the layout
sidebarPanel(
sliderInput(
'shape1',
label = 'Population shape 1:',
min = 1,
max = 9,
value = 2 ,
step = 1
),
sliderInput(
'shape2',
label = 'Population shape 2:',
min = 1,
max = 9,
value = 2 ,
step = 1
),
textInput("n_data", label = "Sample size:",
value = '25'),
textInput("e_samples", label = "number of samples:",
value = '5'),
actionButton("RerunButton", "New sample", icon("play"))
),
mainPanel(plotOutput('Sample'))
))
# Set up the server
server <- function(input, output) {
set.seed(1234)
xvals <- seq(.001, .999, by = 0.001)
# Define reactive values
avgs <- reactiveVal(vector(mode = "list", length = 1))
vals <- reactiveVal(0)
s <- reactiveVal()
sample_plot <- reactiveVal()
# This is where I hope to generate a new graph every second.
observe({
invalidateLater(1000)
cat(paste('vals', vals(), '\n'))
cat(paste('avgs', avgs(), '\n'))
if (vals() < input$e_samples) {
s(data.frame(
d = rbeta(
n = input$n_data,
shape1 = as.numeric(input$shape1),
shape2 = as.numeric(input$shape2)
)
))
temp <- s()
vals(vals() + 1)
averages <- avgs()
averages[vals()] <- mean(temp$d)
avgs(averages)
sample_plot(
ggplot() +
geom_histogram(
data = temp,
aes(x = d),
binwidth = 0.1,
fill = 'white',
col = 'black'
) +
geom_vline(xintercept = mean(temp$d)) +
xlim(0, 1) +
xlab('observation value') +
ylab('count')
)
}
})
output$Sample <- renderPlot({
sample_plot()
})
observeEvent(input$RerunButton, {
vals(0)
})
observeEvent(input$RerunButton, {
avgs(vector(mode = "list", length = 1))
})
}
shinyApp(ui = ui, server = server)
The code above only updates the graph once. Why?

Answer 1

All of your reactiveValues that keep changing are triggering your observe repeatedly right away. This happens five times in succession, well before 1000 msec has elapsed. To prevent this from happening, you would need to use isolate for your reactiveValues. See if this gives the right behavior:
# Set up the server
server <- function(input, output, session) {
set.seed(1234)
xvals <- seq(.001, .999, by = 0.001)
# Define reactive values
avgs <- reactiveVal(vector(mode = "list", length = 1))
vals <- reactiveVal(0)
s <- reactiveVal()
sample_plot <- reactiveVal()
# This is where I hope to generate a new graph every second.
observe({
invalidateLater(1000, session)
#cat(paste('vals', vals(), '\n'))
#cat(paste('avgs', avgs(), '\n'))
if (isolate(vals()) < input$e_samples) {
s(data.frame(
d = rbeta(
n = input$n_data,
shape1 = as.numeric(input$shape1),
shape2 = as.numeric(input$shape2)
)
))
temp <- s()
isolate(vals(vals() + 1))
averages <- isolate(avgs())
averages[vals()] <- mean(temp$d)
avgs(averages)
}
})
sample_plot <- reactive({
ggplot() +
geom_histogram(
data = s(),
aes(x = d),
binwidth = 0.1,
fill = 'white',
col = 'black'
) +
geom_vline(xintercept = mean(s()$d)) +
xlim(0, 1) +
xlab('observation value') +
ylab('count')
})
output$Sample <- renderPlot({
sample_plot()
})
observeEvent(input$RerunButton, {
vals(0)
})
observeEvent(input$RerunButton, {
avgs(vector(mode = "list", length = 1))
})
}