Putting a filter based on a previous filter in Shiny

[kuttan98]

Hi. I am a beginner to R shiny. As practice, I am working on gapminder dataset. I have 2 filters. The first is of continent and second of countries. Once I select a continent, only the relevant countries must appear in the next filter. How can I do this?

library(tidyverse)
library(shiny)
library(shinydashboard)
#> 
#> Attaching package: 'shinydashboard'
#> The following object is masked from 'package:graphics':
#> 
#>     box
library(janitor)
#> 
#> Attaching package: 'janitor'
#> The following objects are masked from 'package:stats':
#> 
#>     chisq.test, fisher.test
library(gapminder)
library(ggthemes)
gapminder<-gapminder %>% clean_names()

ui<-dashboardPage(
  skin="red",
  dashboardHeader(title="Life expectancy across continents",titleWidth = 500),
  dashboardSidebar(selectInput("continent","Select the continent",choices = sort(unique(gapminder$continent)),multiple=T,selected="Asia"),
                   selectInput("country","Select the country",choices=unique(gapminder$country),multiple=T)),
  dashboardBody(
    tabsetPanel(
      type="tabs",
      id="tab_selected",
      tabPanel(title="Continent-view",
               plotOutput("plot1"))
    )
  )
)


server<-function(input,output){
  continent<-reactive({
    gapminder %>% 
      filter(continent %in% input$continent) %>% 
      group_by(continent,year) %>% 
      summarise(mean_exp=mean(life_exp),.groups = "drop") 
  })
  
  output$plot1<-renderPlot({
    ggplot(continent(),aes(year,mean_exp,color=continent))+
      geom_line(size=1.5)+
      theme_minimal()+
      labs(title="How has life expectancy increased across different continents in the post-war period?",x="Year",y="Average Life Expectancy")
  })
}

shinyApp(ui,server)
#> PhantomJS not found. You can install it with webshot::install_phantomjs(). If it is installed, please make sure the phantomjs executable can be found via the PATH variable.
Shiny applications not supported in static R Markdown documents
Created on 2022-03-07 by the reprex package (v2.0.1)

[pieterjanvc]

Hi there,

You can use the updateSelectInput function to change the choices of an input dynamically through the server. Here is an example

library(tidyverse)
library(shiny)
library(shinydashboard)
library(janitor)
library(gapminder)
library(ggthemes)

gapminder<-gapminder %>% clean_names()
#Get all the unique continents and their countries
countryNames = gapminder %>% select(continent, country) %>% 
  distinct() %>% arrange(country)

ui<-dashboardPage(
  skin="red",
  dashboardHeader(title="Life expectancy across continents",titleWidth = 500),
  dashboardSidebar(selectInput("continent","Select the continent",choices = sort(unique(gapminder$continent)),multiple=T,selected="Asia"),
                   selectInput("country","Select the country",choices=c(),multiple=T)),
  dashboardBody(
    tabsetPanel(
      type="tabs",
      id="tab_selected",
      tabPanel(title="Continent-view",
               plotOutput("plot1")),
      tabPanel(title="Country-view",
               plotOutput("plot2"))
    )
  )
)


server<-function(input, output, session){
  
  #Data per continent
  continent<-reactive({
    gapminder %>% 
      filter(continent %in% input$continent) %>% 
      group_by(continent,year) %>% 
      summarise(mean_exp=mean(life_exp),.groups = "drop") 
  })
  
  #Data per country
  countries<-reactive({
    gapminder %>% 
      filter(country %in% input$country) %>% 
      group_by(country,year) %>% 
      summarise(mean_exp=mean(life_exp),.groups = "drop") 
  })
  
  #Change country input optoins if continents change
  observeEvent(input$continent, {
    
    #Filter countries based on current continent selection
    countriesToShow = countryNames %>% 
      filter(continent %in% input$continent) %>% pull(country)
    
    #Update the actual input
    updateSelectInput(session, "country", choices = countriesToShow, 
                      selected = countriesToShow[1])
    
  })
  
  #Plot the continent data
  output$plot1<-renderPlot({
    ggplot(continent(),aes(year,mean_exp,color=continent))+
      geom_line(size=1.5)+
      theme_minimal()+
      labs(title="How has life expectancy increased across different continents in the post-war period?",x="Year",y="Average Life Expectancy")
  })
  
  #Plot the country data
  output$plot2<-renderPlot({
    ggplot(countries(),aes(year,mean_exp,color=country))+
      geom_line(size=1.5)+
      theme_minimal()+
      labs(title="How has life expectancy increased across different countries in the post-war period?",x="Year",y="Average Life Expectancy")
  })
}

shinyApp(ui,server)

I also added a new tab with plot per country so you can see how it would work if you select different countries.

Hope this helps,
PJ

[kuttan98]

Thanks a lot for this. My next objective was to do country-wise tab.