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fit a first,second,and third degree polynomial, and determine the respective regression co-efficients.

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james bond
james bond 2017-12-4
评论： james bond 2017-12-5
i am new to matlab and just need an example to follow, please help Please see attached. thanx
i attempted the first part, plz help with regression...
Time = [1,2,3,4,5,6,7,8,9,10];
Pressure = [26.1,27.0,28.2,29.0,29.8,30.6,31.1,31.3,31.0,30.05];
New_Time = 0:0.5:10;
newf1 = polyval(polyfit(Time,Pressure,1),New_Time);
newf2 = polyval(polyfit(Time,Pressure,2),New_Time);
newf3 = polyval(polyfit(Time,Pressure,3),New_Time);
plot(Time,Pressure,'o',New_Time,newf1,New_Time,newf2,New_Time,newf3)
title('Fit of Pressure Samples')
xlabel('Sample Interval,sec')
ylabel('Pressure, PSI')
legend('Data','Linear Fit','Quadratic Fit','Cubic Fit') % linear is first order, quadratic is second order and cubic is third order

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KSSV
KSSV 2017-12-5
R3 = polyfit(Time,Pressure,3) ;
Gives the coefficients of the polynomial. In this case coefficients of third degree polynomial.
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John D'Errico
John D'Errico 2017-12-5
Calling R^2 a "regression coefficient" is spectacularly poor terminology on the part of the person who wrote that assignment. But, yes, if you need to compute R^2, then you need to use the formula.

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