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How to extract polynomial "p" from symbolic solution "root(p,x,k)"?

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FingersCrossed
FingersCrossed 2022-6-10
评论： Walter Roberson 2022-6-10
When using solve() symbolically and a solution of the form root(f(z),z,k) is produced, is it possible to extract f(z) without manually copying and pasting?
For instance, if I assign an example solution to variable x :
x = root(z^2 + z + 1, z, 1)
Can z^2 + z + 1 or its coefficients be extracted from x?
sym2poly() does not seem to recognize root(). I suppose I could bluntly use regexp(), though it seems there must be a simpler solution.
Related: How to remove "root(f(z), z, n)" from solve solution? - (mathworks.com)

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采纳的回答

Walter Roberson
Walter Roberson 2022-6-10
编辑：Walter Roberson 2022-6-10
use children() — or findSymType() and then children()

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FingersCrossed
FingersCrossed 2022-6-10
Use Walter's answer instead of this. Just for fun, here is a convoluted regexp() approach:
[cell_poly,~] = regexp(string(x),'root\((.*?),','tokens','match');
poly = str2sym(string(cell_poly));

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