How to rename lumped constant terms within parenthesis

Hi Guys

I have some huge symbolic equations (multiple pages) in the variables (x,y,z), of the form:

Eq1(x,y,z) = x*y*(.....) + y*z*x*(....) ....(many pages)

where the brackets contain constant symbolic terms (e.g. they are just constant coefficients), e.g.:

(Q23*l5*l6*m4 + Q22*l5*m4*m6)

Is there anyway to automatically go through each equation and delete / abbreviate the bracketed coefficients to a single letter? Currently I am doing it manually but it takes so long..! Maybe using a find and replace function?

Thanks

Toby

Answer 1

[Walter Roberson]

The easiest way to do this is to go in to the symbolic engine level and use subsex

syms QQ
result = feval(symengine, 'subsex', Eq1(x,y,z), (Q23*l5*l6*m4 + Q22*l5*m4*m6), QQ);

Note that this will be an expression rather than a function. I am not sure if you would be able to execute this on the function returning a function, but you could try -- list Eq1 instead of E1(x,y,z) as the argument.

[Toby Howison]

Many thanks Walter