Problem when plotting points on shiny R with eventReactive - r

Question

This is my first post here so I hope I can explain my problem clearly. I am currently getting into shiny and want to start off by doing basic stuff. I decided to challenge myself by making an app that takes two numeric inputs and plots them whenever I press an actionbar. The problem is that I want to keep the previous points that I plot. I can't get it to work as it keeps resetting the plot. I've tried many different ways and I dont really know how points() works on shiny. Here is the code:
library(shiny)
ui <- fluidPage(
actionButton(inputId="execute",label="Execute"),
numericInput(inputId="numY",label="Y",value=0),
numericInput(inputId="numX",label="X",value=0),
plotOutput("plot")
)
server <- function(input, output) {
coordx <- eventReactive(input$execute,{input$numX})
coordy <- eventReactive(input$execute,{input$numY})
if(!exists("input$execute"))
{
output$plot <- renderPlot({
plot(x=coordx(),y=coordy())
})
}
else
output$plot <- renderPlot({
points(x=coordx(),y=coordy())
})
}
shinyApp(ui = ui, server = server)
Thank you in advance!

Answer 1

As the commenters #Limey and #fvall said, the issue seems to be the eventReactive() which overwrites each time. What I did instead is place the x and y coordinates in a reactiveValues(). Then I placed an observeEvent() for any time input$execute was pressed, writing the x and y coordinates to update the reactiveValues(). This will keep both the old and new values. I also added a little tableOutput() just to keep track of the values:
library(shiny)
ui <- fluidPage(
actionButton(inputId="execute",label="Execute"),
numericInput(inputId="numY",label="Y",value=0),
numericInput(inputId="numX",label="X",value=0),
plotOutput("plot"),
tableOutput("TABLE")
)
server <- function(input, output) {
coord<-reactiveValues("x" = NULL, "y" = NULL)
observeEvent(input$execute, {
req(input$numY, input$numX)
tempx<-c(isolate(coord$x), input$numX)
tempy<-c(isolate(coord$y), input$numY)
coord$x <- tempx
coord$y <- tempy
})
output$plot <- renderPlot({
req(input$execute)
plot(x=isolate(coord$x),y=isolate(coord$y))
})
output$TABLE<-renderTable({
data.frame("x" = coord$x, "y" = coord$y)
})
}
shinyApp(ui = ui, server = server)
Best of luck! Though I had hiccups along the way, I really enjoyed learning Shiny myself, and I hope you do too!