Making E-Analytica Forecasting

Posted on April 24, 2020

E-Analytica Forecasting launched publicly on Monday. It has been a moderate success, at least compared to most of my efforts, with over 150 analyses being conducted since than (not all of them by me!).

Initial Motivation

When doing a forecasting project the value I add comes from customising machine learning models to take into account specifics of the client’s business. But to quantify how much value I’m adding it is necessary to have a baseline to compare with.

Often I would pick a very simple model and run it over the training data to get baseline performance. But there are more complicated models that are just as easy to run as the simple ones so I worried that I was picking a baseline that was, in some way, too easy for me to beat.

I wanted a way of running lots of forecasting models at once and to be able to compare the output in a standard way. This is quite easy for forecasting methods that are part of the forecast package but once you add things like bsts and prophet into the mix this gets more complicated.

I had some functions written to help me do this when (as part of something unrelated) Mark Edmondson pointed out Google Cloud Run to me. I spotted this as an opportunity to run my forecasts in the cloud; everything would automatically be in parallel, it might be useful for getting people up and running in training more easily, and I’d get to learn a new technology too!

Web Frontend

Cloud Run was pleasantly easy to get started with. I was able to turn my old functions into HTTP endpoints using a library called plumber and then it was simply a case of wrapping the whole thing in Docker so that it could run in the cloud.

Cloud Run exposes things as HTTP so once I had things up and running it was a natural next step to start thinking about whether or not it could be used from a web browser.

Shiny is an obvious choice for any kind of web interface to R but I didn’t want to use it for this project for three reasons:

  1. Hosting Shiny apps can be quite tricky. To make things more complicated I wanted the app to be a part of this website which is a static site hosted through Amazon S3 - there isn’t a webserver to hook in with.
  2. When you are on the golden path shiny is A-MA-ZING but as soon as you want to do anything even slightly different it gets very hard. I anticipated not wanting to stay on the golden path for very long.
  3. Shiny communicates with the backend process over websockets and I wasn’t sure how to do this with Cloud Run

I built quite a simple (simple to make, not simple to use!) interface in front of the HTTP API using Elm which enabled people to compare the performance of different forecasting methods on their own data.

Elm did not make integrating with Google Sign In and the Google Analytics API super easily but I got something working in the end so that data can be pulled directly from Analytics. You can see this in action here.

I showed this to some people to see what they thought. Mostly the feedback was “I’m sure this is cool, if you know what it all means”. There was a big gap between what I had built for myself and what others could easily use. I thought my tool would probably be pretty useful during forecasting training sessions where I could be there to explain everything but I was at a bit of a loss how to make the tool easy enough to understand without covering the whole thing in dense text. People don’t read on the internet.


While all this was going on there was quite a lot happening in the outside world!

The UK lockdown on March 24th was catastrophic for some (but not all!) businesses. A lot of plans and activities were put on hold as everyone focused on hunkering down and surviving. During these times a natural question is “how much longer?” I cannot answer this is full but I did notice that it would be possible to repurpose some of my forecasting tools to answer the related question “are things getting better?”

I wanted to make this as quick and simple to use as possible so I only offered the link with Google Analytics and no other way to input data.

I the background, data is fed into prophet but rather than using this to produce a forecast the model is used find out if the trend has changed since lockdown. You can find this tool here


One of the first people to get in touch when I launched on Monday was asking if translation into Polish was on my roadmap. It was not. An localisation of a web app feels like it is well beyond my skillset! I still wanted to help Maciej so I decided to document the HTTP API that runs the backend so that he could present the results in his own language. You can read the API documentation here.

Having an API opens up two potentially bad outcomes:

  1. People will be able to make tens of thousands of requests. If this happened a lot it would increase my compute costs significantly.
  2. People might make something important with the API. And then I would break it if I ever changed anything.

Both of these are actually good things! I’d love it if people built something important off my work. But in order to mitigate the potential downsides I decided to require the use of an API key in order to use the API. The keys are linked with email addresses so I will be able to contact people in the event the API changes.

What Next?

I’m not sure! If you have feedback on the COVID tool then I’d love to hear it. I know I need to make sure things are better explained so that everyone who uses it can feel confident and like they understand what is going on. Machine learning should be empowering rather than something where “computer says no” and people feel like they have lost some agency and control over their work.

I’m also going to keep working on my frontend for comparing forecasting models. I think if I get this right it could be a great way for analysts to do more sophisticated forecasting with a bit more hand holding than they get when staring at a blank R file.