Use selectbox to create regression formula from user input dataset - r

Question

I am attempting to custom build a user-interface regression tool in R shiny for practice (i.e. my own version of spss for my general use-cases). I'm having trouble with the critical step of generating a regression formula from the user-uploaded dataset. I want the user to be able to select a dependent variable from a dropdown menu (and eventually to turn those generated variables into a formula in my server code).
I have tried to use a textOutput(names(userdata())) within the choices argument for a selectInput() function so that the user can select which of their variables should be a dependent variable once they have uploaded their dataset. However, this generates a list of properties of the dataset rather than the names of the columns themselves.
I've looked into other uses of reactive datasets that others have done but no one seems to have done precisely what I am trying to do or I am searching for them badly. (It seems like the most common probable use-case for Shiny, so I can't imagine how no one has figured this out yet, but I can't find anything)
library(shiny)
library(wired)
ui <- fluidPage(
sidebarLayout(sidebarPanel(
fileInput("FileInput", "Input Your Data Set (Must be .csv)"),
wired_select(inputId = "responsevar",
label = "Dependent Varibale:",
choices = textOutput(outputId = "variable_names")
)
), #sidebar panel
mainPanel(
tabsetPanel(
tabPanel("Table",
DT::dataTableOutput("table")
)
) #tabset Panel
) #main panel
) #sidebarlayout
) #fluidpage
server <- function(input, output, session) {
datasetInput <- reactive({
infile <- input$FileInput
if (is.null(infile))
return(NULL)
read.csv(infile$datapath, header = TRUE)
})
output$table = DT::renderDataTable(datasetInput())
output$variable_names <- reactive({
if (is.null(datasetInput()))
return(NULL)
names(datasetInput())
})
} #server
shinyApp(ui = ui, server = server)

Answer 1

textOutput is used to output text to the Shiny UI. This is includes generating appropriate HTML. As wired_select(..., choices = ???) is expecting an R object rather than HTML code this is unlikely to work.
One approach that is likely to work is using updateSelectInput. I do not know whether this has an equivalent function with the wired library, but in base shiny I would:
Initialise the selectInput with no choices
Update the choices in the drop down once the data has been selected
Try the following:
library(shiny)
ui <- fluidPage(
sidebarLayout(sidebarPanel(
fileInput("FileInput", "Input Your Data Set (Must be .csv)"),
selectInput(inputId = "responsevar",
label = "Dependent Varibale:",
choices = NULL)
), #sidebar panel
mainPanel(
tabsetPanel(
tabPanel("Table",
DT::dataTableOutput("table")
)
) #tabset Panel
) #main panel
) #sidebarlayout
) #fluidpage
server <- function(input, output, session) {
datasetInput <- reactive({
infile <- input$FileInput
if (is.null(infile))
return(NULL)
read.csv(infile$datapath, header = TRUE)
})
output$table = DT::renderDataTable(datasetInput())
observeEvent(datasetInput(),{
updateSelectInput(session, "responsevar", choices = names(datasetInput()))
})
} #server
shinyApp(ui = ui, server = server)

Answer 2

Hmm... as the above does not work with the wired library, I'll suggest another possible approach. (I can't install wired in my environment, so apologies if this is no better).
The idea here is to make the selector part of a dynamic R object (a UI object). Then if a file gets loaded, the UI object, which depends on the file, will also update.
library(shiny)
library(wired)
ui <- fluidPage(
sidebarLayout(sidebarPanel(
fileInput("FileInput", "Input Your Data Set (Must be .csv)"),
uiOutput("selector")
), #sidebar panel
mainPanel(
tabsetPanel(
tabPanel("Table",
DT::dataTableOutput("table")
)
) #tabset Panel
) #main panel
) #sidebarlayout
) #fluidpage
server <- function(input, output, session) {
datasetInput <- reactive({
infile <- input$FileInput
if (is.null(infile))
return(NULL)
read.csv(infile$datapath, header = TRUE)
})
output$table = DT::renderDataTable(datasetInput())
output$selector <- renderUI({
choices <- NULL
if(!is.null(datasetInput()))
choices <- names(datasetInput())
wired_select(inputId = "responsevar",
label = "Dependent Varibale:",
choices = choices)
})
} #server
Key differences to my original answer, are uiOutput replacing selectInput and a renderUI output component instead of an observer.