plot dygraph from a list in shiny

Question

I wish to plot xts from a list of xts series by selecting the name of each list. I am not understunding how reactivity and list selection works

library(zoo)
library(dygraphs)
library(xts)

d <- seq(as.Date("2020/01/01"), as.Date("2020/05/01"), "months")
xts1 <- xts(rnorm(5),order.by = d)
xts2 <- xts(rnorm(5),order.by = d)
xts3 <- xts(rnorm(5),order.by = d)
l <- list(xts1,xts2,xts3)
names(l) <- c("uno","dos","tres")

Creation of list of xts objects

library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(

    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            selectInput(names,names,names(l))
        ),

        # Show a plot of the generated distribution
        mainPanel(
            dygraphOutput("plot")
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {
      
    #option 1 
        p <- reactive({
        input$names
    })
   output$plot <- renderDygraph({
        l[[p]]
})

# option 2

    output$plot <- renderDygraph({
        l[[input$names]]
    })
}

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

It doesn´t work neither ways. Appreciate :)

Answer 1

Four things are wrong in your code:

• in selectInput(), you must use quotation marks for the two first arguments, that correspond to inputId and name.

• you can't use output$plot twice in server. plot must be a unique id, so you could have output$plot1 and output$plot2 for instance. This means that you also need to have two dygraphOutput (or plotOutput, or ...) in the ui part.

• when you define a reactive(), you must use parenthesis when you call it afterwards, e.g p() and not p

• in renderDygraph (or renderPlot, or...), you still need to put the code to create the plot, as if it was in regular R and not R Shiny.

Therefore, your corrected code is:

library(zoo)
library(dygraphs)
library(xts)
library(shiny)

d <- seq(as.Date("2020/01/01"), as.Date("2020/05/01"), "months")
xts1 <- xts(rnorm(5),order.by = d)
xts2 <- xts(rnorm(5),order.by = d)
xts3 <- xts(rnorm(5),order.by = d)
l <- list(xts1,xts2,xts3)
names(l) <- c("uno","dos","tres")


# Define UI for application that draws a histogram
ui <- fluidPage(
  
  # Application title
  titlePanel("Old Faithful Geyser Data"),
  
  # Sidebar with a slider input for number of bins 
  sidebarLayout(
    sidebarPanel(
      selectInput("names", "names", names(l))
    ),
    
    # Show a plot of the generated distribution
    mainPanel(
      dygraphOutput("plot1"),
      dygraphOutput("plot2")
    )
  )
)

# Define server logic required to draw a histogram
server <- function(input, output) {
  
  p <- reactive({
    input$names
  })
  output$plot1 <- renderDygraph({
    dygraph(l[[p()]])
  })

  output$plot2 <- renderDygraph({
    dygraph(l[[input$names]])
  })
}

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