How to use poly2list for specific variables?

Hi there,

In the example 2 of the help for 'poly2list' https://www.mathworks.com/help/symbolic/mupad_ref/poly2list.html?s_tid=srchtitle, it shows as follows:

In this example the polynomial is bivariate, thus exponent vectors are returned:

poly2list((x*(y + 1))^2, [x, y])

How to use this in MATLAB? I tried feval but it shows error:

>> syms x y
>> feval(symengine, 'poly2list', (x*(y + 1))^2, [x, y])
Error using mupadengine/feval (line 163)
The number of arguments is incorrect.

Thanks,

Dan

Answer 1

[Walter Roberson]

symLIST = @(varargin)feval(symengine,'DOM_LIST',varargin{:});
feval(symengine,'poly2list',  (x*(y + 1))^2, symLIST(x,y))

[Dan Li]

Thanks very much!

[Walter Roberson]

This is a quite advanced usage, and not many people will understand why it is necessary to do things this way. But it works.

[Dan Li]

Hi Walter,

Thanks for the help.

If I want to store the symbolic variables in a matrix first, how to convert it correctly? For example: X = [x, y], then symLIST(X) will not generate a list of x y but a matrix([[x, y]]). I tried feval(symengine, 'coerce', X, 'DOM_LIST'), but this still not work for the poly2list.

[Walter Roberson]

varcell = num2cell(X);
feval(symengine,'poly2list',  (x*(y + 1))^2, symLIST(varcell{:}))

[Dan Li]

Thanks you very much! This really helps me a lot!

Answer 2

[Karan Gill]

In general, I don't recommend using MuPAD commands, as the note at the top says.

Is coeffs helpful?

>> syms x y
p = (x*(y + 1))^2;
[C,T] = coeffs(p,[x y]) % C = coeffs, T = terms

C =
[ 1, 2, 1]
T =
[ x^2*y^2, x^2*y, x^2]

[Dan Li]

I also want extract the power value of every variable in every monomial. Is there any way to convert the x^2*y^2 to [2, 2]?

Thanks,

Dan