Want Function: Derivation of (x) returns a function of dx (euler-lagrange equation problem)

Hello, I am trying to derive equations, in such a way that the returned function is a function of the derivative of the variable I derive for. i.e. diff(f(x))= f(dx).

Example:

f(x) = 2x

deriveVariable = x

I want:

 someFunction(f(x),deriveVariablle) = 2*dx.

I need this because I am deriving positions and velocities, and therefore need the returned equation to be a function of the derivative of the variable I derive for, instead of it being truncated as the function diff() does.

Is there any way to do this? I am using MatLab R2013a.

My goal is to use matlab to solve euler-lagrange equation(below) for the dynamics of a robotic arm system. If there is another simpler way to directly do that, that would solve my problem as well.

euler-lagrange equation =

(d/dt)*((partialDerivative*f(x))/ (partialDerivative ((d/dt)*x))) -

((partialDerivative*f(x))/ (partialDerivative x))

Thanks a bundle

Answer 1

[Mischa Kim]

Matt, there are a couple of tools for deriving Lagrange's equations on File Exchange.