Multiple variables to facet_wrap from selectInput: R Shiny

Question

I am seeking some help for my Shiny App with facet_wrap(). I have some data & I want the app to dynamically facet_wrap with one or more variables selected from a single selectInput. App does it with only one variable but not with multiple. When I select multiple variables from the same selectInput, only first variable is considered for faceting in the plots. I do not want to use facet_grid(). There are two things What I want help on.

When the app begins for the first time, I get the error 'Error: invalid first argument'. How to get rid of this error.
How to facet plots with multiple variables selected from single selectInput. Any suggestion or help is much appreciated.

Repex code:

library(shiny)
library(tidyverse)
library(DT)
# Define UI for data upload app ----
ui <- fluidPage(
    titlePanel("Upload & View Files"),
      sidebarLayout(
        sidebarPanel(width = 2,
          selectInput("facet", "Select Facets", choices = colnames(data), "", multiple = T)
  ),
    
    # Main panel for displaying outputs ----
    mainPanel("Data View",
      plotOutput("heatmap", width = "1050px", height = "800px"),
      DT::dataTableOutput("table")
      
    )
    
  )
)

# Define server logic to read selected file ----
server <- function(session, input, output) {
  data <- diamonds
   output$table  <- DT::renderDataTable(data, options = list(paging = T, pageLength = 20))
   output$heatmap <- renderPlot({
     ggplot(data, aes(x = carat, fill = carat)) + geom_bar() + facet_wrap(~ get(input$facet), scales = "free")
   })
  }
shinyApp(ui, server)

What I looking at is when multiple variables are selected from the selectInput; Ex: cut, clarity, depth etc. It would be like having facet_wrap(~ cut + clarity + depth, scales = "free)

Error Message Multiple Facet required

score 2 · Accepted Answer · answered May 22 '21 at 17:43

2

To remove the error, use req(). For multiple selected variables, one way is shown below. There may be a better way to do it.

output$heatmap <- renderPlot({
    req(input$facet)
    
    facets <- input$facet %>% 
      str_replace_all(",", "+") %>% 
      rlang::parse_exprs()
    
    ggplot(data, aes(x = carat, fill = carat)) + geom_bar() +
      facet_wrap(vars(!!!facets), scales = "free")
    
  })

answered May 22 '21 at 17:43

YBS

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Hi YBS, thanks for your response. It does work the way I needed. Appreciate it. – Sandeep Patil May 24 '21 at 07:17
It is considered polite to accept an answer that has answered your OP. This helps others who are looking for a solution for the same/similar query. Furthermore, people may be willing to help you in your future queries. – YBS May 24 '21 at 11:26

Multiple variables to facet_wrap from selectInput: R Shiny

1 Answers1