For example, I have a polynomial y＝a_0＋a_1 x + ..... + a_50 x^50. Since I know that the high-order terms are imposing negligible effects on the evaluation of y, I want to ignore them and have something like y＝a_0＋a_1 x , the first eleven terms. How can I do this in Matlab?
I thank you all in advance.
You can use polyfit and specify the order of polynomial (n). in your example, the value n is set to 10. type "doc ployfit" for more info. You should use appropriate statistical methods to choose a good value for n
[p,S] = polyfit(x,y,n) returns the polynomial coefficients p and a structure S for use with polyval to obtain error estimates or predictions.
y = polyval(p,x) returns the value of a polynomial of degree n evaluated at x. The input argument p is a vector of length n+1 whose elements are the coefficients in descending powers of the polynomial to be evaluated
Where do these polynomial terms originate from, expansion series? And do you know exactly terms to ignore?
You can use polyfit and specify the order of polynomial (n). in your example, the value n is set to 10. type "doc ployfit" for more info. You should use appropriate statistical methods to choose a good value for n
[p,S] = polyfit(x,y,n) returns the polynomial coefficients p and a structure S for use with polyval to obtain error estimates or predictions.
y = polyval(p,x) returns the value of a polynomial of degree n evaluated at x. The input argument p is a vector of length n+1 whose elements are the coefficients in descending powers of the polynomial to be evaluated
Dear @Najmeh, if you are interested in just chopping the last terms of the polynomial then you can follow the answer that is given by dear Professor @Behrouz; if you want to use the most impacting factors of the polynomial then you have to take a look at the Greedy Algorithm. See the link:
https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Greedy_algorithm.html
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