NumericInput takes a random sample - is this even possible?

[erinjohnson]

I'm trying to build an app so the user can upload data in the UI, then draw a random sample from it based on a characteristic of the data, then download the sample they made.

Once the data table is uploaded, is it possible for a numeric input to take a sample of it?

So if I upload the location of all of the grocery stores in Nebraska, and want a random sample of 10 from zipcode 68503, would I start by filtering for 68503 then have my (theoretical) sample input then a "generate" button?

The people I'm working with were doing this all back-end in SAS using surveyselect.

I think this project was out of my league....any ideas would be appreciated, informative links are super double appreciated.

This is the only code I have so far. Again, ANY help is appreciated

library(shiny)
library(DT)

Define UI for data upload app ----

ui <- fluidPage(

# App title ----
titlePanel("Project Extra Mile List Generator"),

# Sidebar layout with input and output definitions ----
sidebarLayout(
    
    # Sidebar panel for inputs ----
    sidebarPanel(
     
        # Input: Select a file ----
        fileInput("file1", "Choose CSV File",
                  multiple = FALSE,
                  accept = c("text/csv",
                             "text/comma-separated-values,text/plain",
                             ".csv")),
        # Button
        actionButton("update", "Generate", 
                     class = "btn-primary",style='padding:4px; font-size:120%')
        
    ),
    
    # Main panel for displaying outputs ----
    mainPanel(
        
        # Output: Data file ----
        DTOutput("contents")
        
    )
)

)

Define server logic to read selected file ----

server <- function(input, output) {

#Table
output$contents <- renderDT({
    
    req(input$file1)
    
    df <- read.csv(input$file1$datapath)    
    
})

}

Create Shiny app ----

shinyApp(ui, server)

[pieterjanvc]

Hi,

Although the question seems easy it required quite some Shiny tricks to get the desired result.
Here is the app I made (read comments how to generate sample data)

library(shiny)
library(DT)

ui <- fluidPage(
    sidebarLayout(
        
        # Sidebar panel for inputs ----
        sidebarPanel(
            
            # Input: Select a file ----
            fileInput("file1", "Choose CSV File",
                      multiple = FALSE,
                      accept = c("text/csv",
                                 "text/comma-separated-values,text/plain",
                                 ".csv")),
            
            selectInput("variable", "Choose variable", choices = ""),
            selectInput("subset", "Choose subset", choices = ""),
            numericInput("nSamples", "How many random samples?", value = 1),
            
            # Button
            actionButton("update", "Generate", 
                         class = "btn-primary",style='padding:4px; font-size:120%'),
            
            downloadLink("downloadData", "Download")
            
        ),
        
        # Main panel for displaying outputs ----
        mainPanel(
            
            # Output: Data file ----
            DTOutput("contents")
            
        )
    )
)

server <- function(input, output, session) {
    
    #Uncomment, Run and delete these two commented lines of code to get sample file to test...
    # df = data.frame(ID = 1:10, zip = c(rep(68503, 5), rep(45763, 5)))
    # write.csv(df, "testData.csv", row.names = F)
    
    df = reactiveVal()
    randomSubset = reactiveVal()
    
    #Change the variables based on the columns in the file
    observeEvent(input$file1, {
        df(read.csv(input$file1$datapath))
        updateSelectInput(session, "variable", choices = colnames(df()))
    })
    
    #For the selected variable, display all different options
    observeEvent(input$variable, {
        updateSelectInput(session, "subset", choices = unique(df()[,input$variable]))
    })
    
    #On update, pick n samples from the selected sub category
    observeEvent(input$update, {
        randomSubset(df()[eval(parse(text = paste("df()$",input$variable, "==", input$subset, sep = ""))),])
        randomSubset(randomSubset()[sample(1:nrow(randomSubset()), input$nSamples), ])
        output$contents <- renderDT({
            randomSubset()
        })
    })
    
    #Download csv when completed
    output$downloadData <- downloadHandler(
        filename = function() {
            paste("randomSample.csv", sep="")
        },
        content = function(file) {
            write.csv(randomSubset(), file, row.names = F)
        }
    )

}

shinyApp(ui, server)

It should work, but beware I did NOT implement any error handling, meaning that if a user uploads a wrong file or tries to pick too many random samples from a dataset that doesn't have them, the app will crash.

Lemme know what you think...

PJ

[erinjohnson]

Hi PJ,

THANK YOU SO MUCH. This is everything, this is exactly what I needed!! I can't believe it!! I've been stuck on this for MONTHS. Is there anything I can do to give you credit when I turn this in? I'm so incredibly appreciative of your help.

Erin

[pieterjanvc]

Hi Erin,

I'm happy it solved your problem! Honestly, your genuine praise is more than enough credit Just label my answer as the solution and I'm good.

In case you need some extra help, feel free to send me a message here.

Grtz,
PJ