obtaining coeff. of syms function

I m solving a 4th order eqn using syms, its like a*x^4+b*x^3+c*x^2+d*x+e=0, where a,b,c,d,e are constants. the eqn is stored in syms as 1x1 sym . I want to obtain the coeff.(a,b,c,d,e) separately from the sym structure.

Answer 1

[Paulo Silva]

a=1;b=2;c=3;d=4;e=5;
syms x
s=a*x^4+b*x^3+c*x^2+d*x+e
c=coeffs(s)

The c vector is what you want, the index values are in reverse order so

c=fliplr(c)

c(1) is your a c(2) is your b ...

just noticed that c is also symbolic so if you want the numeric values do

double(c)

[ajit bhuddi]

thanks a lot

It works quite well.

Answer 2

[ajit bhuddi]

But I want to add some more thing to the answer

if the equation is for example: g=ax^3+bx^2+c

coeffs(g) will return only [c,b,a] and it will not give coeff. corresponding to coeff. of x (which is 0 in this case).

[Paulo Silva]

That's completely different from your original question but I will help you once more:

a=1;b=2;c=3;

syms x

s=a*x^3+b*x^2+c

pf=sym2poly(s);

pf(end-1) %the coefficient for x

[ajit bhuddi]

this seems fine for a more general polynomial case.