I posted this question on Software Recommendations. As it is getting no response, I think that I might try to make a meaningful chart for my friend, in Excel .
Actually, I would prefer someone else to post an Excel formula to do so, but that is certainly off-topic here.
What I am hoping is not off topic is asking for a mathematical formula which will produce meaningful results.
From that question:
Basically my friend weighs daily and has historical data in CSV format. They would like a gratis app that takes that data and overlays 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.
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 days can be identified as problematic then the cause can be identified and behavio(u)r changed.
So, could I somehow phrase that to be an on-topic question here? I am looking for a pattern in data (and how best to represent it visually).