Asking for a friend, who has read [this](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5644907/).

Basically my friend weighs daily and has historical data in CSV format. They would like to take that data and overlay it in some form of weekly chart. E.g shows only Monday to Sunday (start day preferably selectable), not several months or years.

We are unsure what format the display should take, but the objective is to see if there is a pattern to weight loss/gain on certain days of the week (e.g, every Tuesday).

My friend has been steadily losing weight for months now, but against that background, there are days when weight is gained and my friend is looking for an identifiable pattern. A very obvious example would be weight gain on Monday after a weekend binge, but this is not the case, just an example. The idea is that if certain weekdays can be identified as problematic then the cause can be identified and behavio(u)r changed.

I could probably manage to create an Excel chart from the data, but how to identify any patterns, probably based on day of the week?