# L2 - norm help

1. Mar 6, 2010

### mcooper

Could someone please explain to me in fairly basic terms what the L2-norm is and what it does please. More specifically let me know what the following equation does...

E(N) = 2*pi$$\int$$(u(N) - uexact)2 r dr

Where E is the error for a specific N. I haven't found any good resources for learning about this on the internet. Also if someone could recommend a good book that would be great.

2. Mar 6, 2010

### BSCowboy

I know of $$l_p$$ spaces. For $$0\leq p<\infty$$ it's the set whose elements are sequences of scalars $$x=\{\lambda_1, \lambda_2, \ldots, \lambda_n,\ldots\}$$ such that $$\left(\sum|\lambda_n|^p\right)^{\frac{1}{p}}$$ is convergent.