.. _plumber:

APIs from R models with plumber
===============================

Let's assume you've written a complex model in R that can predict whether a
person is a cat person or a dog person:

.. code-block:: R

  cats.vs.dogs <- function(firstName, lastName) {
    if (lastName %in% c('Schrodinger', 'Schrödinger', 'Schroedinger')) {
      return('cat')
    }
    else {
      return('dog')
    }
  }

In order to deploy this model as an API, we are going to use `plumber
<https://www.rplumber.io/>`__, an R framework that parses code and turns
functions decorated with special comments into API endpoints.

Save the following in a file called ``api.R`` in the root of your project:

.. code-block:: R

  # api.R

  #' @post /predict
  cats.vs.dogs <- function(firstName, lastName) {
    if (lastName %in% c('Schrodinger', 'Schrödinger', 'Schroedinger')) {
      return('cat')
    }
    else {
      return('dog')
    }
  }

We can now create our API. Go to the APIs page for your project in Faculty
and create a new API. You will be asked to choose a name, a domain name and a
type for your API. For type, choose Plumber (R). Your domain name needs to be
unique across all of Faculty. I suggest a domain name like cats-vs-dogs-2118,
where you replace 2118 with a random string of your choice.

In the API settings page, change the working directory to /project, and the
plumber file to ``api.R``. You can leave the `environments` dropdown empty.

.. thumbnail:: images/plumber-configuration.png

After you have your API set up, you can test and ultimately deploy it. Head to
:ref:`develop-api` to find out how to go about the testing process.

Once you are familiar with the API development process, you may want to write a
more complex API. Take a look at these examples below for inspiration:

.. toctree::
  :titlesonly:

  multiple_endpoints_plumber