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matlabsymbolic-math

How to store Taylor series coefficients into an array in Matlab script

This question is in the context of a .m script.

I know how to get the Taylor series of a function, but I do not see any command that allows one to store the series' coefficients into an array – sym2poly does not seem to work.

How does one store coefficients into an array? For example, this function:

syms x
f = 1/(x^2+4*x+9)

How would we be able to get the Taylor coefficients? fntlr did not work.

Solution

  • Using your example, the symbolic taylor and coeffs functions can be used to obtain a vector of coefficients:

    syms x
f = 1/(x^2 + 4*x + 9);
ts = taylor(f,x,0,'Order',4) % 4-th order Taylor series of f about 0
c = coeffs(ts)

    which returns

    ts =

(8*x^3)/6561 + (7*x^2)/729 - (4*x)/81 + 1/9


c =

[ 1/9, -4/81, 7/729, 8/6561]

    Use vpa or double to convert c to decimal or floating point.