R Shiny: updateSelectInput based on reactive dataframe - r

Question

I have a shiny app where a user filters the article column of my dataset depending on the articles he wants to see. Those articles are then displayed in a table. The articles react as actionbutton with a custom function on a click.
I want that whenever a user clicks on a certain article, this article is selected in selectInput. Nevertheless I have no idea which value to pass to the selected attribute of updateSelectInput.
I have put three question marks in the place where I am stuck. By removing the three questionmarks the code is executable.
Any help appreciated
library(shiny)
library(tidyverse)
library(kableExtra)
library(formattable)
df = tibble(article=c("one", "two", "three", "four", "five", "six"),
group=c("a", "a", "a", "b", "b", "b"),
sales=c(12,13,14,43,50,45))
ui = fluidPage(
sidebarPanel(
radioButtons(inputId = "select_a", label = "Choose a group", choices = unique(df$group), selected = "a"),
htmlOutput(outputId = "table")),
sidebarPanel(
selectInput(inputId = "select_b", label = "Choose an article", choices = df$article, selected = "one")
)
)
server = function(input, output, session){
shinyInput <- function(FUN, len, id, labels, ...) {
inputs <- character(len)
for (i in seq_len(len)) {
inputs[i] <- as.character(FUN(paste0(id, i), label = labels[i], ...))
}
inputs
}
df_reactive = reactive({
df %>% filter(group == input$select_a) %>%
mutate(article = shinyInput(actionButton, n(), 'button_', labels = article, onclick = 'Shiny.onInputChange(\"select_button\", this.id)'))
})
output$table = function(){
df_reactive() %>%
kable("html", escape = F, align = "c") %>%
kable_styling(bootstrap_options = c("striped", "condensed", "responsive"), full_width = F, position = "center") %>%
scroll_box(width = "100%", height = "auto")
}
observeEvent(input$select_button, {
updateSelectInput(session = session, inputId = "select_b", selected = ???)
})
}
shinyApp(ui = ui, server = server)

Answer 1

Perhaps you can use this.innerText to retrieve the article here:
mutate(article = shinyInput(actionButton, n(), 'button_', labels = article,
onclick = 'Shiny.onInputChange(\"select_button\", this.innerText)'))
And then input$select_button will contain the text string to select:
updateSelectInput(session = session, inputId = "select_b", selected = input$select_button)