How to separate negative and positive terms in to two different expressions

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EllaD
EllaD 2020-12-3
评论： Ameer Hamza 2020-12-3
I am using symolic vavriables
syms a b c d f g
Where all syms variables are positive
and have, for example the following expression A
F=a- b*d+ g*c-a*c+ d*g
my actual expression is much longer but how can I separate the negative vs the positive terms and put them in say in x and y?
I appreciate any help .
Thank you!

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Ameer Hamza
Ameer Hamza 2020-12-3
Try this
syms a b c d f g
F = a - b*d + g*c - a*c + d*g;
parts = children(F);
parts = [parts{:}];
assume(symvar(parts)>0)
sgns = sign(parts);
assume(symvar(parts), 'clear')
x = parts(sgns==1);
y = parts(sgns==-1);
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EllaD
EllaD 2020-12-3
gives this:
Error using cellfun
Input #2 expected to be a cell array, was sym instead.
Error in negativepositive (line 17)
sgns = cellfun(@sign, parts);
it is 2012a . But thanks anyways Ameer :) I will be going for an upgrade, it is way old I guess.
Ameer Hamza
Ameer Hamza 2020-12-3
Yes, it seems something related to old release. It seems that children() does not return a cell array in your case.

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