How to make an interactive chart for varying input variables using highcharter in shiny

Question

In R, I would like to create a highcharter chart which displays varying combinations based on the user input from a select input field. However, I keep on failing with this.

I have got two input fields where both input fields have two opportunities. The user can select either combination and the selected variable should be used for a scatter plot in Highcharter. I tried quite some opportunities however it does not work.

xvar <- input$varx
yvar <- input$vary

hc <-   chart_df %>%
    hchart('scatter',
       hcaes(x = xvar,
             y = yvar,
             names = xvar),
       dataLabels = list(enabled = TRUE,
                         format = '{point.names}')
)

However, it does not recognize the assigned xvar and yvar. The data frame chart_df contains the respective columns. How could I solve this? Any help would be appreciated!

Answer 1

The issue is that xvar and yvar are strings. To make your code work you have to convert them to symbols using eg !!sym() or use hcaes_string which like ggplot2::aes_string allows you to pass variables as characters.

Using mtcars as example data set try this:

library(shiny)
library(highcharter)
library(rlang)

ui <- fluidPage(

    sidebarLayout(
        sidebarPanel(
            selectInput("varx",
                        "varx",
                        choices = names(mtcars),
                        selected = "hp"),
            selectInput("vary",
                        "vary",
                        choices = names(mtcars),
                        selected = "mpg")
        ),

        # Show a plot of the generated distribution
        mainPanel(
            highchartOutput("highchart"),
            highchartOutput("highchart2")
        )
    )
)

server <- function(input, output) {

    output$highchart <- renderHighchart({
        
        xvar <- input$varx
        yvar <- input$vary
        
        hc <-   mtcars %>%
            hchart('scatter',
                   hcaes(
                       x = !!sym(xvar),
                       y = !!sym(yvar),
                       names = !!sym(xvar)),
                   dataLabels = list(enabled = TRUE,
                                     format = '{point.names}')
            )
    })
    
    output$highchart2 <- renderHighchart({
        
        xvar <- input$varx
        yvar <- input$vary
        
        hc <-   mtcars %>%
            hchart('scatter',
                   hcaes_string(
                       x = xvar,
                       y = yvar,
                       names = xvar),
                   dataLabels = list(enabled = TRUE,
                                     format = '{point.names}')
            )
    })
}

shinyApp(ui = ui, server = server)