app.R

#
# This is a Shiny web application. You can run the application by clicking
# the 'Run App' button above.
#
# Find out more about building applications with Shiny here:
#
#    http://shiny.rstudio.com/
#

library(shiny)
library(ggplot2)

data_url <- "https://arcticdata.io/metacat/d1/mn/v2/object/urn%3Auuid%3A35ad7624-b159-4e29-a700-0c0770419941"
bg_chem <- read.csv(url(data_url, method="libcurl"), stringsAsFactors = FALSE) %>% 
    select(-Date, -Time, -Station)

cols<-names(bg_chem)

# Sometimes you need to wrap the web address in url() on some platforms
#bg_chem <- read.csv(url(data_url, method = "libcurl"), stringsAsFactors = FALSE), different computers handle downloading data from the web in different ways, in windows read.csv does not know how to deal with https servers, so url function, tells windows to use a different method to deal with https urls, giving windows more instruction

names(bg_chem)

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

    # Application title
    titlePanel("Water Biogeochemistry"),

    # Sidebar with a slider input for number of bins 
    verticalLayout(
        sidebarLayout(
            sidebarPanel(
                sliderInput("depth",
                            "Depth:",
                            min = 0,
                            max = 500,
                            value = c(0,100))
            ),
            
            # Show a plot of the generated distribution
            mainPanel(
                plotOutput("distPlot")
            )
        ),
        sidebarLayout(
            sidebarPanel(
               selectInput("x_variable","X Variable", cols, selected = "CTD_Salinity"),
               selectInput("y_variable","Y Variable", cols, selected = "d18O"),
               selectInput("color_variable","Color", cols, selected = "P"),
            ),
            
            # Show a plot of a selectd set of variables
            mainPanel(
                plotOutput("varPlot")
            )
        )
    )
)

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

    output$distPlot <- renderPlot({
        ggplot(bg_chem, mapping = aes(x=CTD_Depth, y = CTD_Salinity))+
            geom_point(color='red', size = 4) +
            xlim(input$depth[1], input$depth[2])+
            theme_light()
    })
    output$varPlot <- renderPlot({
        ggplot(bg_chem, mapping = aes_string(x=input$x_variable, y = input$y_variable, color = input$color_variable))+
            geom_point(size = 4) +
            scale_color_gradient2(low="midnightblue",
                                  mid="white",
                                  high="firebrick", 
                                  midpoint=mean(bg_chem[,input$color_variable]))+
            theme_light()
    })
}

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