crunch + shiny = crunchy

crunchy makes it easy to build Shiny apps with data stored in the Crunch.io cloud data service. You can run these apps locally, or you can host them on Crunch.

Installing

Install crunchy from CRAN with

install.packages("crunchy")

The pre-release version of the package can be pulled from GitHub using the remotes package:

# install.packages("remotes")
remotes::install_github("Crunch-io/crplyr")

Using

Load library(crunchy) and it brings with it both the shiny and crunch packages. Most things in a Crunchy app work just as they would in a Shiny app or as they would working with Crunch in an interactive R session, with a couple of exceptions. Most importantly, you should not login() to Crunch as you would otherwise do when using the crunch R package. Your Crunchy app will use the authentication token from the web browser, the one you get when you log into the Crunch web app.

crunchy provides a few important functions to facilitate building Shiny apps with Crunch data and managing authentication and authorization:

• Wrap crunchyServer() around your usual shiny::shinyServer() function to enforce Crunch authentication and to be able to supply custom authorization rules, which you can set with setCrunchyAuthorization().
• Wrap crunchyBody() around your UI body (inside shiny::shinyUI(), the part after any tags$head() or other headers) to conditionally show your app when the current user is authenticated. Add crunchyPublicBody() to specify what unauthenticated users will see, and crunchyUnauthorizedBody() for what authenticated but not authorized users will see.
• To report a Shiny progress bar for any Crunch requests that show a text progress bar in R, wrap the code in withCrunchyProgress().

In addition, there are a couple of functions that return reactive versions of Crunch objects:

• shinyDataset(), a wrapper around crunch::loadDataset() that returns a reactive object
• shinyUser() similarly returns the (reactive) Crunch entity of the current user

Their reactivity responds to the current user of the Crunchy app, concerned with the use case of deploying Crunchy apps at shiny.crunch.io for users that may have different authorization. Note that, because shinyDataset returns a shiny reactive object, you need to always “call” it when you want to get the dataset in your server function scope. Your server function might look something like:

function(input, output, session) {
    ds <- shinyDataset("Your dataset name")

    freqs <- reactive({
        fmla <- as.formula(paste("~", input$varname))
        crtabs(fmla, data=ds())
    })
    ...
}

Note ds() instead of just ds in the aggregation function.

You are recommended to load datasets in your Crunchy app by their API URL, not by their name or path. This is the fastest, most reliable way to reference a dataset–the dataset’s URL will never change and is the same for everyone.

For a simple example of a Crunchy app that shows interactive summary plots for variables, copy system.file("example_apps/crunchy_server/app.R", package="crunchy"), supply your dataset id on line 14, and run it.

Running your app locally

If you have not done so already, go to https://app.crunch.io and log in to the Crunch web app. This will set an authentication cookie in your browser. You’ll need this to be able to access your datasets in your Crunchy app.

In addition to installing the crunchy package and its dependencies (including a suitable version of R), you’ll need to add an entry to your /etc/hosts file that maps localhost to local.crunch.io. You probably already have a line in there like 127.0.0.1 localhost, so you can add local.crunch.io as an alias after localhost on the same line. (This works slightly differently on different operating systems; consult Google if you aren’t sure how to do it on yours.) This host file mapping is needed to allow you to use your cookie from app.crunch.io.

Serve your app as you would any other Shiny app. There are a number of ways to do this; one example, for a directory named “demo” containing server.R and ui.R files, you can run this from the command line:

$ R -e 'library(crunchy); runApp("demo", port=7765)'

substituting the port of your choice, or omitting the port argument entirely if you want Shiny to choose a free one for you. The host file mapping lets you access this app at http://local.crunch.io:7765, and because the domain matches the Crunch service at app.crunch.io, your authentication cookie from there works, and you will be able to load and query your datasets.

Deploying your app

You can host Crunchy apps at shiny.crunch.io and use them as dashboards within the Crunch web app. See the wiki for instructions on setting up and maintaining apps.

For package contributors

The repository includes a Makefile to facilitate some common tasks, if you’re into that sort of thing.

Running tests

$ make test. Requires the httptest package. You can also specify a specific test file or files to run by adding a “file=” argument, like $ make test file=server. test_package will do a regular-expression pattern match within the file names. See its documentation in the testthat package.

Updating documentation

$ make doc. Requires the roxygen2 package.