Short course on Shiny

[Andrea]

Hi all,

I would like to follow a (short, because I'm short on free time ) online course on Shiny. I had a look at the shiny category here, but the Shiny developers web series seems a bit too high-level for me (I'm not exactly looking to build "intricate Shiny apps", more like connecting to some remote data source & showing the results in some dashboard )

[andresrcs]

This is actually pretty simple to do (If you don't currently have the time, you don't even need to take a course for this), I think that a simple example would take you pretty close and you can work from there, this is a simplified version of an app that I use to monitor my internet connection speed.

library(shinydashboard)
library(odbc)
library(tidyverse)
library(tibbletime)
library(glue)

# reactivePoll update functions
last_timestamp <- function(){
    sql_query <- "select max(time) as current_time from public.speed_test"
    dbGetQuery(con, sql_query)[1,1]
}

update_data <- function(){
    sql_query <- "SELECT * FROM public.speed_test ORDER BY time"
    dbGetQuery(con, sql_query)
}

# Database connection
connection_string <- glue("Driver={{PostgreSQL ANSI}};\\
                            Uid={Sys.getenv('MY_UID')};\\
                            Pwd={Sys.getenv('MY_PWD')};\\
                            Server={Sys.getenv('MY_REMOTE')};\\
                            Port=5432;\\
                            Database=movistar;")
con <- dbConnect(odbc::odbc(), .connection_string = connection_string, encoding = "utf8")

# UI
ui <- dashboardPage(skin = "black",
                    dashboardHeader(title = "Internet Speed"),
                    dashboardSidebar(disable = TRUE),
                    dashboardBody(
                        fluidRow(
                            box(plotOutput('speed_plot'),
                                width = 12
                            )
                        )
                    )
)

# Server response
server <- function(input, output, session) {
    
    # Check for new data every 5 seconds
    pollData <- reactivePoll(5000, session,
                             checkFunc = last_timestamp,
                             valueFunc = update_data
    )
    
    # Connection speed plot
    output$speed_plot <- renderPlot({
        pollData() %<>%
            tail(24) %>% 
            as_tbl_time(index = time) %>% 
            collapse_by('1 hour', side = 'start', clean = TRUE) %>% 
            gather(type, speed, Download, Upload) %>%
            ggplot(aes(x = time, y = speed)) +
            geom_line(aes(color = type)) +
            geom_point() +
            labs(title = 'Connection Speed',
                 subtitle = "Last 24 hours",
                 x = 'Time',
                 y = 'Speed (Mbits/s)',
                 color = 'Traffic Type:') +
            scale_x_datetime(date_breaks = "1 hour",
                             date_labels = '%b-%d %H:%S',
                             expand = c(0.01,0.01)) +
            scale_y_continuous(breaks = seq(0, 22, by = 2), limits = c(0, 23)) +
            NULL 
    })
}

onStop(function() {
    # Close connection on exit
    dbDisconnect(con)
})

shinyApp(ui, server)

[Andrea]

Thanks! I'll try it out and let you know how it works for me!

[woodward]

This example did not run for me. Is it using a local database?

Error: nanodbc/nanodbc.cpp:950: IM002: [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified 

[andresrcs]

It is just a coding example, not a reproducible one, obviously you have to connect to your own database (or API), I could upload some data to a sandbox database and make it reproducible but I honestly see no point on it. (Andrea is not a beginner, I'm sure he can get the pattern and apply it to his own application)