What is centering of data




The highlighted portion mentions that data should be internally centered as this allows much faster convergence of the algorithm.I understand that if data is centered the number of iterations required will be less but what is centering of data?


Centering simply means subtracting a constant from every value of a variable. What it does is redefine the 0 point for that predictor to be whatever value you subtracted. It shifts the scale over, but retains the units.
The following deals with the ways in which centering can be done:

The following deals with why it isn’t always a good idea to center/standardize the data:

Hope this helps!