Getting Started with Regression in R

Regressions are widely used to estimate relations between variables or predict future values for a certain dataset. If you want to know how much of variable "x" interferes with variable "y" you might want to do a regression in your data. If you have a bunch of data points in time, and you want to know what is your data going to look like in the future, you also might want to do regression. I will try to describe the steps that helped me successfully build linear and non-linear regression in R, using polynomials and splines. I am not going to go on too much details on each method.