xfit = linspace(T(1),T(end),100);
%px = polyfit(T,P,3);
[px,S] = polyfit(T,P,3);
%yfit = polyval (px,xfit);
[yfit,delta] = polyval (px,xfit,S);
plot(xfit,yfit,'b-') % Plot conditioned fit vs. x data
hold on
yupper = (yfit+delta);
ylower = (yfit-delta);
plot(xfit,yupper,'r')
plot(xfit,ylower,'r')