How do you deal with IDs in Shiny Dropdown lists? - r

Question

Typically in a web interface if you have a dropdown populated from a database that display's some text and you want to use that selected text in the dropdown and pass it back to a database. But a lot of times you want to pass an ID instead of the actual text displayed.
In my example below I have a global.R file that returns the data for the dropdowns. This simulates data returned from a database. For each dropdown there is a text field that is displayed in the dropdowns and an "id" field that is not displayed BUT I have to somehow access the "id" fields of the dropdowns. How is this done in Shiny?... Because the selectInputs don't allow you to store the ids so you can access them like input$DisplayName$id
In the example below I just want to print the "id" of the "DisplayName" selectInput so if "Mary" is in the input$DisplayName then "20" should be printed in the RenderText call.
Here is code to run:
require(shiny)
runApp(list(
ui = basicPage(
sidebarPanel(
selectInput("Department", "Select a department", choices = as.character(GetDepartments()$Department), selected = as.character(GetDepartments()$Department[1])),
uiOutput("DisplayName")
),
mainPanel(textOutput("Text") )
),
server = function(input, output, session) {
output$DisplayName<-renderUI({
Department <- input$Department
print(Department)
selectInput("DisplayName", 'DisplayName:', choices = as.character(GetDisplayName(Department)$DisplayName), selected =as.character(GetDisplayName(Department)$DisplayName[1] ))
})
output$Text <- renderText({
# Here I want to simulate accessing the "id" field of the input$DisplayName
#in my app I need to pass the id to a database query
#If Mary is in input$DisplayName how can I access her id of "20"?
print("in render text")
return( ??? How do I access the id = 20???)
})
}
))
Here is the global.r file that simulates code that returns stuff from a database
GetDepartments<- function(){
df<- data.frame(Department= c("Dept A", "Dept B"), id = c(1,2))
return(df)
}
GetDisplayName<- function(Dept){
if(Dept == "Dept A")
{
df<- data.frame(DisplayName= c("Bob", "Fred"), id = c(4,6))
return(df)
}else
{
df<- data.frame(DisplayName= c("George", "Mary"), id = c(10,20))
return(df)
}
}

Answer 1

This is very similar to your other question here. As #nrussel suggests, this is just a simple subsetting problem. Just pull up your department and index on the name. Here is a working example.
EDIT*** - make dataset reactive to avoid repetition.
As per the documentation:
Reactive expressions are a smarter than regular R functions. They cache results and only update when they become obsolete. The first time that you run a reactive expression, the expression will save its result in your computer’s memory. The next time you call the reactive expression, it can return this saved result without doing any computation (which will make your app faster). The reactive expression will use this new copy until it too becomes out of date.
runApp(list(
ui = basicPage(
sidebarPanel(
selectInput("Department", "Select a department",
choices = as.character(GetDepartments()$Department),
selected = as.character(GetDepartments()$Department[1])),
uiOutput("DisplayName")
),
mainPanel(textOutput("Text") )
),
server = function(input, output, session) {
myData <- reactive({
GetDisplayName(input$Department)
})
output$DisplayName<-renderUI({
Department <- input$Department
print(Department)
myData <- myData()
selectInput("DisplayName", 'DisplayName:', choices = as.character(myData$DisplayName),
selected =as.character(myData$DisplayName[1] ))
})
output$Text <- renderText({
print("in render text")
myData <- myData()
code <- as.character(myData[myData$DisplayName == input$DisplayName,2])
return(code)
})
}
))