Shiny reactive input for multiple input selectors

[Dawie]

Hope someone can help me.

I'm building an app that requires multiple input selectors that needs to filter as the selection continues. I've made an example below. I think that the code goes into a loop but can't figure out what the solution is. I've looked for similar examples but spent way too much time on this problem.

Please assist.

Code:

pacman::p_load(shiny, tidyverse)

mtcars_df <- rownames_to_column(mtcars, "model")

# Define UI for application that draws a histogram
ui <- fluidPage(
    checkboxGroupInput(
        "select_cyl",
        "Select cylinder: ",
        choices = mtcars_df$cyl %>% unique(),
        selected = mtcars_df$cyl %>% unique()),
    checkboxGroupInput(
        "select_model",
        "select model: ",
        choices = mtcars_df$model %>% unique(),
        selected = mtcars_df$model %>% unique()
    ),
    plotOutput("hist_hp")
)

# Define server logic required to draw a histogram
server <- function(input, output, session) {
    mtcars_reactive <- reactive({
        filter(mtcars_df, 
               cyl %in% input$select_cyl,
                model %in% input$select_model)
    })
    
    observe({
        x <- mtcars_reactive() %>% pull(model) %>% unique()
        
        updateCheckboxGroupInput(session = session,
                          "select_model",
                          choices = x,
                          selected = x)
    })
    
    output$hist_hp <- renderPlot({
        
        x <- mtcars_reactive()
        
        hist(x$hp)
    })
    

}

# Run the application 
shinyApp(ui = ui, server = server)

[bretauv]

I think it is because you use updateSelectInput instead of updateCheckboxGroupInput

[Dawie]

Thank you, I've updated the code to updateCheckboxGroupInput but a new problem surfaced. When I make changes to the selection on the cyl selection then the model changes does happen but only once. Second time the there is no change. It must be a reactive issue?

[Dawie]

Can anyone assist me with this problem on reactivity? The list does not remain reactive once a selection was made.

[KWANGER]

This may not be the best approach... but it's the way I know how to do it and it works for me:

pacman::p_load(shiny, tidyverse)

mtcars_df <- rownames_to_column(mtcars, "model")

Define UI for application that draws a histogram

ui <- fluidPage(
checkboxGroupInput(
"select_cyl",
"Select cylinder: ",
choices = mtcars_df$cyl %>% unique(),
selected = mtcars_df$cyl %>% unique()),

uiOutput("model"),
plotOutput("hist_hp")
)

Define server logic required to draw a histogram

server <- function(input, output, session) {

datasub<-reactive({
foo <- subset(mtcars_df, cyl == input$select_cyl)
return(foo)
})

output$model<-renderUI({
selectizeInput("select_model","select model:",
choices = unique(datasub()$model),
selected = unique(datasub()$model[1]))
})

datasub2<-reactive({
foo<-subset(datasub(),model == input$select_model)
return(foo)

})

output$hist_hp <- renderPlot({

x <- datasub2()

hist(x$hp)

})

}

Run the application

shinyApp(ui = ui, server = server)

Let me know if this isn't what you were looking for!