Make the intercept of the linear fitting equals zero

[BorjaRuizReverter]

It is evident, @SandroRob, that Surface equals zero for a cylindrical object with radius zero. In other words, we have to be certain that the intercept of the linear fitting is zero, because, otherwise, it could affect the experimental value of PI.

Therefore, please add this as experimental data in the tables.

Before that, however, wait until @IsabeliSouto, insert the tables into the jupyter notebook.