Saving a polynomial function

Question

Mak Dukan 2021-11-1

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1576833-saving-a-polynomial-function

回答： Walter Roberson 2021-11-1

Hi all,

I have a simple question. How can I save a polynomial function? By this I mean somethign like "p(x)=p1xn+p2xn−1+...+pnx+pn+1", however with all the coeficients and powers? I need to fit multiple curves and would like to avoid having to type the equation every single time.

Here is the code I am using for an example:

p = polyfit(CapFac_DEAll_2019_sorted,HornsRevB_Prc_sort,5);
y1 = polyval(p,CapFac_DEAll_2019_sorted);
Fig1 = figure('Name','HornsRevB vs All DE for 2019');
scatter(CapFac_DEAll_2019_sorted, HornsRevB_Prc_sort,16,'r');
hold on
plot (CapFac_DEAll_2019_sorted,y1,'--b');
hold off

As you can see I am using first polyfit and then polyval to plot the curve and see if its a good fit.

I need these functions to multiply other timeseries values with them.

Thanks,

Mak

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Answer 1

Walter Roberson 2021-11-1

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1576833-saving-a-polynomial-function#answer_821743

Just save the p variable. It is an ordered list of coefficients, highest degree first. You can use polyval() and polyder()

If you have the symbolic toolbox, you an also use poly2sym() to get an expression that you could either save or use matlabFunction() with (possibly with the 'File' option.)