Multi scale analysis using mathematica

[nickthequick]

I am doing multi scale analysis while solving a particular nonlinear PDE. I am trying to check a solution I have for a particular set of boundary conditions and governing equation, to a given order.

Is there a simple way to sort scales on Mathematica? For example, if our small parameter is a, and I just want to check the O(a^3) solution, is there a way I can have Mathematica set all higher order terms to zero? Even a way to present the solution in such a way that terms are grouped by their polynomial (in a) degree. Manual inspection could work, but my equations are complex and my output is ~ 75 pages.

Any help is appreciated!

Thanks,

Nick

 

[Dale]

Series[f, {x, x0, n}] generates a Taylor series expansion of f[x] to order O(x-x0)^n