R Shiny: Create a button that updates a data.frame - r

Question

I have a randomly generated data.frame. The user can modify a slider to choose the number of points. Then I plot this data.frame.
I want to add a button than when clicked, it performs a modification in the previous randomly generated data.frame (but without regenerating the data.frame). The modification is a voronoid relaxation, and it should be performed once per each time the button is clicked and the graph generated.
Until now, I have not achieved anything similar...
ui.R
library(shiny)
# Define UI for application that draws a histogram
shinyUI(fluidPage(
# Application title
titlePanel("Map Generator:"),
# Sidebar with a slider input for the number of bins
sidebarLayout(
sidebarPanel(
p("Select the power p to generate 2^p points."),
sliderInput("NumPoints",
"Number of points:",
min = 1,
max = 10,
value = 9),
actionButton("GenPoints", "Generate"),
actionButton("LloydAlg", "Relaxe")
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("distPlot",height = 700, width = "auto")
)
)
))
server.R
library(shiny)
library(deldir)
shinyServer(function(input, output) {
observeEvent(input$NumPoints,{
x = data.frame(X = runif(2^input$NumPoints,1,1E6),
Y = runif(2^input$NumPoints,1,1E6))
observeEvent(input$LloydAlg, {
x = tile.centroids(tile.list(deldir(x)))
})
output$distPlot <- renderPlot({
plot(x,pch = 20,asp=1,xlim=c(0,1E6),ylim = c(0,1E6))
})
})
})
Of course there is something that I must be doing wrong, but I am quite new into shiny I can't figure it out what I am doing wrong...

Answer 1

This should work (even though I am pretty sure this could be improved):
shinyServer(function(input, output) {
library(deldir)
data = data.frame(
X = runif(2^9, 1, 1E6),
Y = runif(2^9, 1, 1E6)
)
rv <- reactiveValues(x = data)
observeEvent(input$GenPoints, {
rv$x <- data.frame(
X = runif(2^input$NumPoints,1,1E6),
Y = runif(2^input$NumPoints,1,1E6)
)
})
observeEvent(input$LloydAlg, {
rv$x = tile.centroids(tile.list(deldir(rv$x)))
})
output$distPlot <- renderPlot({
plot(rv$x,pch = 20,asp=1,xlim=c(0,1E6),ylim = c(0,1E6))
})
})
So first I initialize the points to plot. I use runif(2^9, 1, 1E6) because the starting value of the sliderInput is 9 all the time.
I also removed the observeEvent from the sliderInput and moved it to the GenPoints actionButton.