Shiny actionbutton to set a customized default - shiny

Question

In this shiny App (code below), I need that the button labeled 'Customized' returns:
Select var X: disp
Select var Y: drat
Point size: 1.0
This necessity is a bit similar to the reset button available on the R package 'shinyjs', with the diference of that the reset button returns to the code's default.
library(shiny)
library(shinyjs)
shinyApp(
ui <- fluidPage(
sidebarPanel(
fluidRow(
shinyjs::useShinyjs(),
id = "panel_vars",
# Buttons
uiOutput("varx"),
uiOutput("vary"),
numericInput("ptSize", "Point size",
min=.1, max=5, value = 2),
actionButton("p1", 'Reset variables XY'),
helpText(""),
actionButton("p2", 'Customized')
)
),
mainPanel(
plotOutput("plot")
)
),
server <- function(input, output) {
getModel <- reactive({
names(mtcars)
})
output$varx <- renderUI({
selectInput("varsel.x", "Select var X",
choices = as.list(getModel()), multiple = F)
})
output$vary <- renderUI({
selectInput("varsel.y", "Select var Y",
choices = as.list(getModel()), multiple = F)
})
observeEvent(input$p1, {
shinyjs::reset("panel_vars")
})
output$plot <- renderPlot({
p <- mtcars %>% ggplot(aes_string(x=input$varsel.x, y=input$varsel.y))+
geom_point(size=input$ptSize)
p
})
}
)

Answer 1

You can simply use updateSelectInput and updateNumericInput to do so:
library(shiny)
library(shinyjs)
library(dplyr)
library(ggplot2)
shinyApp(
ui <- fluidPage(
sidebarPanel(
fluidRow(
shinyjs::useShinyjs(),
id = "panel_vars",
# Buttons
uiOutput("varx"),
uiOutput("vary"),
numericInput("ptSize", "Point size",
min=.1, max=5, value = 2),
actionButton("p1", 'Reset variables XY'),
helpText(""),
actionButton("p2", 'Customized')
)
),
mainPanel(
plotOutput("plot")
)
),
server <- function(input, output,session) {
getModel <- reactive({
names(mtcars)
})
output$varx <- renderUI({
selectInput("varsel.x", "Select var X",
choices = as.list(getModel()), multiple = F)
})
output$vary <- renderUI({
selectInput("varsel.y", "Select var Y",
choices = as.list(getModel()), multiple = F)
})
observeEvent(input$p1, {
shinyjs::reset("panel_vars")
})
output$plot <- renderPlot({
req(input$varsel.x,input$varsel.y,input$ptSize)
p <- mtcars %>% ggplot(aes_string(x=input$varsel.x, y=input$varsel.y))+
geom_point(size=input$ptSize)
p
})
observeEvent(input$p2, {
updateSelectInput(session,'varsel.x',selected = 'disp')
updateSelectInput(session,'varsel.y',selected = 'drat')
updateNumericInput(session, "ptSize", value = 1.0)
})
}
)