Hiya,

The idea is good I agree. Here are my comments.

1. Regression using 4 data points might cause fitting problems. For example, for different values of S you might end up with final answer.
2. Also, you will ask the app user to do 4 trails. It is always better to ask for only 1 trial.
3. You can try neural networks in python and later embed them using any Android IDE.
4. You can also go for sparsity promoting techniques and then using a symbolic regression for obtaining symbolic equations in different scenarios and the use just the ‘if else’ in your app code.
5. My final suggestion is that you should go for some complex algorithm like fully connected layers in order to account for accuracy and user feasibility.

Thanks

Prakhar