How do I plot only a couple terms with the coefficients from a fit?

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MathWorks Support Team 2015-11-19

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https://ww2.mathworks.cn/matlabcentral/answers/256492-how-do-i-plot-only-a-couple-terms-with-the-coefficients-from-a-fit

回答： MathWorks Support Team 2015-11-19

I have a model function which consists of many terms. Let GG be the cfit results. Using

feval(GG, xdata)

gives the fit using all the terms. Is it possible to plot only a couple terms, e.g. Term 3 + Term 4, without fitting the model function again?

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Answer 1

MathWorks Support Team 2015-11-19

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Yes. The following example plots the linear terms of a polynomial fit of census data.

load census;
GG = fit(cdate,pop,'poly3','normalize','on');
coeff = coeffvalues(GG);
normedData = (cdate - mean(cdate)) / std(cdate); % coefficients were derived in fit with normalized xdata so normalize it to plot
Y = coeff(3)*normedData + coeff(4); % fit using only the linear terms
scatter(normedData, pop);
hold on
plot(normedData, Y); % plot linear terms