%Problem 6
%Use Matlab polyfit function
%*********************************************************************
function[]=problem6()
%transpose of stock information
yData=y';
xData=1:1:67;
%*******************************************
%best least-squares line, 1 indicates a LINE
%*******************************************
plot(xData, yData, 'o'); hold on
p=polyfit(xData, yData,1);
 
%plot information
xPlot = 1:1:67;
yPlot = polyval(p, xPlot);
plot(xData, yData, 'b', xPlot, yPlot, 'v')
 
%*******************************************
%CUBIC, 3 indicates a cubic
%******************************************
p=polyfit(xData, yData, 3);
 
%plot information
yPlot=polyval(p, xPlot);
plot( xPlot, yPlot, 'd');
 
%*******************************************
%degree 8 approx polynomials, 
%*******************************************
p=polyfit(xData, yData, 8);
 
%plot information
yPlot=polyval(p, xPlot);
plot(xPlot, yPlot, 'g');
 
%*******************************************
%using the SPLINE function on every 6th point in yData
%*******************************************
counter=1;
yData2=zeros(1,12);
%extract every 6 element out of the original data array
for i=1:6:67
    yData2(counter)=yData(i);
    counter=counter+1;
end
xData2=1:6:67;
tt=1:0.1:67;
 
%find x piece
xPlot2=ppval(spline(xData2,yData2), tt);
 
%plot
plot(tt, xPlot2, 'r'); 
hold off
end