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Topic: get coefficients from a symbolic polynomial
Replies: 6   Last Post: Jan 5, 2013 5:49 PM

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Nasser Abbasi

Posts: 6,677
Registered: 2/7/05
Re: get coefficients from a symbolic polynomial
Posted: Jan 5, 2013 5:02 PM
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On 1/5/2013 3:49 PM, Qiming wrote:

> Hi Nasser:
> Thanks for your reply.
> In your case, actually only 'x' is symbolic, the coefficients 0,1,2,3 are already
>in numerical form. But my question is: what if 0,1,2,3 are all in symbolic forms?
> I only give a simple example so that you might think why can't I
>directly put 0,1,2,3 in the expression. However, in my real application,
>those coefficients long and complicated and are generated by MATLAB symbolic
>tool box. I just want to "retrieve" those coefficients for my future use. Of
>course I can check those coefficients from the command window, but I
>don't want to put them back in my code by hand.
> Qiming

why is it so hard for someone to just make a simple example to explain
what they mean? one spends so much time writing words, instead of
making a simple code example.

If you mean this:

EDU>> syms x a b
EDU>> y=a*x^2+b*x+1;

then do

EDU>> coeffs(y,x)
[ 1, b, a]

If you still mean something else, then make up a small example. Do not
explain in words, show a small Matlab example of the input polynomial
itself. complete and self contained example. I am sure you can make
one up if you try.


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