Apply simplify on individual coefficients after using the collect function

14 次查看（过去 30 天）
Fabrice Demière
Fabrice Demière 2017-12-23
评论： Tom Teasdale 2022-8-9
Hello everyone,
I have a complicated symbolic expression that I want to rewrite in terms x and y. So I use: collect(expression,[x,y])
I obtain some result in the form of c1*x+c2*y. Now I want to simplify the c1 and c2 coefficients while still retaining the collected form. Is there any way to do this? When I use simplify, it cancels the collecting of the terms.
I saw that is was possible to write : collect(expression,[x,y],simplify) in MuPad, but it doesn't seem to work in Live scripts.
Thanks!

请先登录，再回答此问题。

采纳的回答

Walter Roberson
Walter Roberson 2017-12-23
No, there is not.
However, if you are fairly sure about the form of your expression, you can use coeffs to pull out the c1 and c2, which you would then be able to simplify and then reconstruct the expression.
You could also consider using children(). Unfortunately at the MATLAB level, when you use children() you cannot find out what the connecting operator is between the children -- unlike MuPAD. Doing any substantial symbolic Mathematics programming requires the ability to examine the operators such as _plus or atan2 to figure out which situation you are facing, but unfortunately the MATLAB level does not currently have any ability to give you this information short of using evalin(symengine) or fevel(symengine) to have MuPAD break up the expression for you.
  1 个评论
Tom Teasdale
Tom Teasdale 2022-8-9
Perhaps this function might help some people, it does what Fabrice asked. It just assumes that an equation is passed and that the children of the equation are summands.
function eqn = simplifyCollect(eqn, expr, steps)
%SIMPLIFYCOLLECT Collects expression and simplifies collected children.
arguments
eqn sym
expr sym
steps (1,1) {mustBePositive} = 1
end
eqn = collect(eqn, expr);
c = children(rhs(eqn));
for i = 1:numel(c)
exp = c{i};
exp = simplify(exp, 'Steps', steps);
c{i} = exp;
end
eqn = lhs(eqn) == collect(sum([c{:}]), expr);
end

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Common Operations 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by