computing a regression polynomial of degree 2

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Anas Gharsa il 26 Gen 2022
Commentato: Anas Gharsa il 26 Gen 2022
I want to compute a regression polynomial for some datapoints and than estimate the value of the function at another datapoint!! i wrote something that gives me 0 error but the graph is not ok!! this is what i wrote
x= [0.9 1.5 2.4 2.6 2.8 3.1 3.5 3.8]; %Data points
y= [1.0 0.8 1.3 6.2 9.3 6.0 2.1 -0.5];
p1 = polyfit(x,y,2); %The regression polynomial of degree 2
yest = polyval(p1,2.5);
xfit = linspace(0,length(x),8);
yfit = polyval(p1,xfit);
plot(x,y,'o',xfit,yfit,'-');
hold on
p2 = polyfit(x,y,7); %The regression polynomial of degree 7
yest2 = polyval(p2,2.5);
xfit1 = linspace(0,10,8);
yFit1 = polyval (p2,2.5);
plot(x,y,'b',xfit1,yFit1,'--');
hold on
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Torsten il 26 Gen 2022
You didn't substitute xfit1=x.
Anas Gharsa il 26 Gen 2022
Thank you so much !!!

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