How to add interactive scaling on Shiny dual Y axis graph line-CodePudding

I'm trying to make an interactive graph in Shiny where you can use a slider to change a scaling value for one of the lines on a dual Y axis graph. Here is what the base graph looks like

The code I am using to plot the graph in Shiny is below, my aim was to define the "coeff" variable as the input of a slider in the UI, and to then incorporate this into how the values of the line were calculated

###Shiny dual Y axis plot

library(shiny)
library(ggplot2)

ui <- fluidPage(
  titlePanel("Line Graph"),
  sidebarLayout(
    sidebarPanel(
      sliderInput("scalegvt","Scale Government Data by:",  min = 0.03, max = 1.0, value = c(1.0))
    ),
    
    mainPanel(
      plotOutput("distPlot")
    )
  )
)

## Creating server logic
server <- function(input, output) {
  coeff <- reactive({
    req(input$scalegvt)
  })
  output$distPlot <- renderPlot({ #Rendering plot
    compggp <- ggplot(NULL, aes(x = date, y = covid))  
      geom_spline(data = onsdf, 
                  aes(x = date, y = covid, colour = "ONS Modelled Estimates"), nknots = 90, size = 1.3)  
      geom_spline(data = gvtdf, 
                  aes(x = date, y = covid/coeff, colour = "Gvt Reported Positive Tests"), nknots = 90, 
                  size = 1.3)##This is the section I want to make reactive to "coeff"##
    
    #Stringency bars
    compggp <- compggp   purrr::pmap(strindf, barfunction)
    
    #Adding aesthetics
    compggp <- compggp   scale_x_date(limits = as.Date(c("2020-05-03", NA )))  
      theme_minimal()  
      scale_y_continuous(labels = scales::comma)  
      labs(x = "Date (year - month)", y = "Covid Cases (estimated and reported)")   
      scale_y_continuous(labels = scales::comma, name = "Modelled Population Estimates", 
                         sec.axis = sec_axis(~.*coeff, name = "Reported Positive Tests"))  
      scale_colour_manual(name = "",
                          values = c("ONS Modelled Estimates"="khaki4", 
                                     "Gvt Reported Positive Tests" = "darkcyan",
                                     "Lockdown Stringency" = "red"))
    compggp
  })
}

# Running application
shinyApp(ui = ui, server = server)

I'm not actually getting any error messages from this code; the slider and the graph both render properly but just don't interact with each other.

Many thanks!

CodePudding user response：

Thanks to @YBS, coeff() solved it