Update specific row and column of dataframe - r

Question

I'm trying to store user input into a pre-existing dataframe in shiny.
In this simplified example I have a dataframe with a column labelled 'colour' and I want radio choice buttons to be able to assign values to each row in the dataframe, starting with row 1, then row 2 then row 3 etc. But it seems the dataframe always resets to the original value. What am I misunderstanding about shiny here?
library(shiny)
library(tidyverse)
library(DT)
dataframe <- tibble(row_id = c(1,2,3),
colour = c("","",""))
ui <- fluidPage(
radioButtons("colour",
"Pick a colour:",
choices = c("blue","green","red")),
actionButton("next_button", "Pick the next colour"),
DTOutput("dataframe")
)
server <- function(input, output) {
vals <- reactiveValues(active_row = 1)
observeEvent(input$next_button,{
dataframe[vals$active_row, "colour"] = input$colour
# view(dataframe)
# print(vals$active_row)
vals$active_row = vals$active_row + 1
output$dataframe <- renderDataTable(dataframe)
})
}
# Run the application
shinyApp(ui = ui, server = server)

Answer 1

I would store your data also in reactiveValues. In addition, you can move your output outside of your observeEvent. This server function should work based on your description.
server <- function(input, output) {
vals <- reactiveValues(active_row = 1, data = dataframe)
observeEvent(input$next_button,{
vals$data[vals$active_row, "colour"] = input$colour
vals$active_row = vals$active_row + 1
})
output$dataframe <- renderDataTable(vals$data)
}