sfit data array output

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Hi, I have this:

SS_fit_Xs=fit(Wave_length,real_Solar_spectrum,'poly9');

then I can plot it so easily like this:

plot(SS_fit_Xs,Wave_length,real_Solar_spectrum);

but to get fitted curve as data I have to write down very long formula with 10 coefficients.

Is there any way to do it in a shorter line?

thanks

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Asliddin Komilov 2019-10-6

在 MATLAB Online 中打开

ASTMG173.xls

now I have this

A=xlsread('ASTMG173.xls');
real_Solar_spectrum=A(:,3);%W/m2
Wave_length=A(:,1)./1e9;% m
SS_fit_Xs=fit(Wave_length,real_Solar_spectrum,'poly9');
SS_fit=SS_fit_Xs(1)*Wave_length.^9+SS_fit_Xs(2)*Wave_length.^8 ...
+SS_fit_Xs(3)*Wave_length.^7+SS_fit_Xs(4)*Wave_length.^6 ...
+SS_fit_Xs(5)*Wave_length.^5+SS_fit_Xs(6)*Wave_length.^4 ...
+SS_fit_Xs(7)*Wave_length.^3+SS_fit_Xs(8)*Wave_length.^2 ...
+SS_fit_Xs(9)*Wave_length+SS_fit_Xs(10);

and SS_fit doesn't look even close to real_Solar_spectrum.

can you help?

thanks

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Answer 1

darova 2019-10-6

在 MATLAB Online 中打开

0 个投票

This code

A = xlsread('ASTMG173.xls');
x = A(:,1);
y = A(:,3);
plot(x,y)

Produces

Is it the curve you want to approximate?

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Asliddin Komilov 2019-10-7

编辑：Asliddin Komilov 2019-10-7

yes, but rather x = A(:,1)./1e9, since it makes the difference in fit.

darova 2019-10-7

Is it the way the approximated curve should looks like?

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sfit data array output

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