To show, for the `tomato' data, the effect of finding a line fit

% M-file = toms.m

%

% To show, for the `tomato' data, the effect of finding a line fit (not sorting data), then aquadratic fit (not sorting data) and finally a quadratic fit (sorting data). Clearly for a quadratic fit, the sorting is essential! For the linear fit it is not essential because the line, though drawn as a zigzag, still looks like a line.



tomato

C=polyfit(x,y,1);

Y=polyval(C,x);

plot(x,y,'*w',x,Y,'w')

xlabel('This is the linear fit, without sorting')



pause



C=polyfit(x,y,2);

Y=polyval(C,x);

plot(x,y,'*w',x,Y,'w')

xlabel('This is the quadratic fit, without sorting!')



pause



[sx i]=sort(x);

sy=y(i);

C=polyfit(sx,sy,2);

Y=polyval(C,sx);

plot(sx,sy,'*w',sx,Y,'w')

xlabel('This is the quadratic fit, WITH sorting')