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I built a Google Sheets add-on that makes it easy to produce forecasts on time series datasets directly inside your spreadsheet.

Story behind it - more than a year ago, a friend of mine asked me to produce some forecasts on some (legal) drug sales data. I don’t have the Office suite on my machine, so I tried using Google Sheets. But Google Sheets’ built-in FORECAST function didn’t work because the data had seasonality. I checked out other Google Sheets add-ons, none did the job well either (please correct me if I’m wrong!).

The only way I could make it work is by creating the forecast in Python. I found it a hassle, but had other projects so I set the idea aside.

One year later, I decided to look into building add-ons for Google Workspace, and remembered this idea. There was a lot of trial and error, as the documentation can be quite confusing sometimes. Nevertheless, the add-on's finally been listed on the Google Workspace Marketplace: https://workspace.google.com/marketplace/app/forecastsheets/...

(I put the link to my landing page in the Show HN because I find the marketplace listing UI hard to read).

The add-on is very basic at the moment. The prediction algorithm uses the Holt-Winters exponential smoothing method, with an additive trend component and an additive seasonal component. There are no other options for the model, and no other models either.

The add-on's free, but to be fully transparent I'll probably have a premium version, subscription-based, where you can do more stuff in the add-on.

In terms of who might use this - I'm thinking mainly that it's people in data analytics, marketing, maybe high-volume sales. I've kept it fairly generic in case I discover other applications.

I'm looking for feedback so I know whether it's worth developing it further. Totally fine if not. Either way, let me know what y'all think of it!