functionalDerivative, deriving as function of derivative?

Hello all,

I'm attempting to compute a Lagrangian EQs of motion.

Part of this requires computing the partial derivative of L with respect to variable_dot, the derivative of the variable.

syms t m1 m2 x1(t) x2(t) k

K = (1/2)*m1*diff(x1,t)^2;

P = (sym(1)/2)*k*(x1-x2)^2;

L = K - P

diff( functionalDerivative( L, diff(x1)) ,t) - functionalDerivative(L,x1)

functionalDerivative() does not like the form of the "diff(x1)". Is there a way to do this?

Thanks a lot, Dan

Answer 1

[John BG]

Takeshita san has a detailed explanation how to solve the Euler-Lagrange equation with MuPAD:

http://uk.mathworks.com/matlabcentral/fileexchange/42196-euler-lagrange-equation?s_tid=srchtitle

If you find this link useful, please click on the thumbs-up vote link above,

thanks in advance

John

[e-mail]

[Dan D]

I was hoping that the new functionalDerivative() function would make this a little cleaner. it works great for the partial derivative in respect to x(t), it just doesn't seem to be able to handle diff(x(t)) as a parameter.