Update a data frame in shiny server.R without restarting the App

r, shiny

Solution

If you just update regular variables (in the global environment, or otherwise) Shiny doesn't know to react to them. You need to use a `reactiveValues` object to store your variables instead. You create one using `reactiveValues()` and it works much like an environment or list--you can store objects by name in it. You can use either `$foo` or `[['foo']]` syntax for accessing values.

Once a reactive function reads a value from a `reactiveValues` object, if that value is overwritten by a different value in the future then the reactive function will know it needs to re-execute.

Here's an example (made more complicated by the fact that you are using `load` instead of something that returns a single value, like `read.table`):

values <- reactiveValues()
updateData <- function() {
  vars <- load(file = "my_data_frame.RData", envir = .GlobalEnv)
  for (var in vars)
    values[[var]] <- get(var, .GlobalEnv)
}
updateData()  # also call updateData() whenever you want to reload the data

output$foo <- reactivePlot(function() {
  # Assuming the .RData file contains a variable named mydata
  plot(values$mydata)
}

We should have better documentation on this stuff pretty soon. Thanks for bearing with us in the meantime.

Problem

Any ideas on how to update a data frame that shiny is using without stopping and restarting the application? I tried putting a `load(file = "my_data_frame.RData", envir = .GlobalEnv)` inside a reactive function but so far no luck. The data frame isn't updated until after the app is stopped.

Original source