Smoothing in charts, useless?

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ecerulm
ecerulm Registered Posts: 45 ✭✭

 The Line > Smoothing option gives some weird artifacts with loops and multiple values of Y for a single value of X, which I found hilarious :

Pasted_Image_2023-08-28__13_20.jpg

The same line chart without smoothing.

Pasted_Image_2023-08-28__13_23.jpg

I'm guessing it's some kind of bezier curve but doing something with the control points that I don't understand.

Does anybody know for sure that kind of smoothing are they applying here?

and isn't there a more appropriate form of smoothing/ curve-fitting for this context, like regular spline smoothing?

Any way I created a Product Idea https://community.dataiku.com/t5/Product-Ideas/Implement-more-sensible-line-smoothing-algorithms/idi-p/37056 to ask for support of other "smoothing" techniques

In case anyone want to reproduce it, I attached the dataiku_smoothing.csv file to this post. You just need to create a project > Dataset > New dataset > Upload your files > dataiku_smoothing.csv

Then navigate to the Dataset > Charts and add

* Show Y : quantity (AVG)

* By X: order_date (automatic)

The Lines > Smoothing (is on by default)

The result is

Pasted_Image_2023-08-28__14_43.jpg

Answers

  • Alexandru
    Alexandru Dataiker, Dataiku DSS Core Designer, Dataiku DSS ML Practitioner, Dataiku DSS Adv Designer, Registered Posts: 1,209 Dataiker
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    Hi @ecerulm
    ,

    As mentioned in the support ticket on this topic, charts smoothing use a policy that avoids overstepping the real bounds of the data on the Y axis, as this would lead to creating wrongful min and max. One drawback of this policy is that it indeed can create artefacts on the X axis. You need to disable smoothing if you want to ensure no artefacts can occur, neither or X nor Y.

    We've taken note of this feature request.

    Thanks,

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