Data splitting with createDataPartition dynamically choosing the variable to split the data around

Question

I have a method where I want to split my data depending on a variable.

My code looks like this:

split_data <- eventReactive(input$split_btn, {
    req(input$variables)
    
    set.seed(123)
    createDataPartition(data()$Survived, p = input$split_percent, list=FALSE)
  })
  
  train_data <- reactive({
    data()[split_data(), ]
  })
  
  test_data <- reactive ({
    data()[-split_data(), ]
  })

This works perfectly, I have a slider that chooses the % of the split and updates it whenever I move It.

The problem comes when I try to use a selectInput to choose between my variables instead of just putting "Survived" since I want ppl that use my app to choose it freely.

selectInput("variable", "Seleccione la variable target:",
                    choices = names(data())),

createDataPartition(data()$input$variable, p = input$split_percent, list=FALSE)

These don't work and I get this error:

Warning: Error in createDataPartition: y must have at least 2 data points

I tried using as.name() and .data[[]] around my input, but it does not work.

There is something I'm missing about using dynamically selected variables in other functions that require it since I had other problems previously