Ragu Pappu Technical thoughts, mostly

Interactive Dublin (California) Weather Visualization Using Shiny

A few weeks back I wrote a post in which I visualized Dublin (CA) 2014 weather in Edward Tufte's style of New York 2003 weather visualization. That post used a dataset containing 15 years of daily weather data from 2000 to 2014 and showed daily temperature highs and lows against a background of daily record highs and lows and average highs and lows of years before 2014. I wanted to write an interactive application using Shiny, RStudio's web application framework for R, and the Dublin weather visualization seemed like a great candidate. I wrote the Shiny app and in the chart below you see the app in action -- an interactive version of that visualization. The user can select the range of years of temperature data to form the background, anywhere between years 2000 and 2014 inclusive.

The above app is hosted on my account at shinyapps.io. The code for it is located here.

Code Changes

A Shiny app requires a minimum of two code modules named ui.R and server.R. I got started writing the app by copying those two modules from lesson 2 of the RStudio Shiny tutorial to my local folder and then making the necessary changes.

I added a sliderInput user-interface to allow the user to select the start_year to bracket data upto and including 2014. By default the weather visualization displays the daily record highs and lows and also the daily average highs and lows in the background. I added two checkboxInputs to allow the user to hide those background displays. The code for the original visualization post used a file, viz_temps.R, which I re-used for this post but with several changes to allow it to work within the Shiny framework. I converted the R script in that file into a function called viztemps() which is invoked from server.R.

The code changes in ui.R and server.R were simple and straightforward as you can see below. Other code modules are not shown (they are located here).



# Define UI for application

  # Application title
  titlePanel("Dublin (California) 2014 Temperatures"),

  # Show a plot of the generated distribution


  # Sidebar with a slider input for the number of bins
      h4("Data Range (Start Year to 2014)"),
                  'Select StartYear',
                  min = 2000,
                  max = 2014,
                  value = 2004),
      checkboxInput('hide_hilows', 'Hide background daily record highs and lows bars'),
      checkboxInput('hide_avgs', 'Hide background average daily highs and lows bars'),



# Preprocessing and summarizing data

# Visualization development

# For text graphical objects (to add text annotation)


# Define server logic required to draw a histogram
shinyServer(function(input, output) {

  output$DublinTemps <- renderPlot({

In order to get it to run on this webpage I simply embedded within this post's markdown file an HTML iframe tag using the code below

<iframe src="https://ragupappu.shinyapps.io/shiny-dublin-temps/" style="border: none; width: 100%; height: 700px"></iframe>

NOTE: Sometimes it can take up to a minute to draw the chart when the page first loads. But it can also take that much time to re-draw when the user changes slider settings or selects/unselects checkboxes. At the time of posting this article I know of no way to speed up the drawing. If you know how to do it, please post in the comments section.