Polyval input when manual value

Hi, I create a first 3*5 matrix using polyfit() corresponding to 3 curves

for xx=1:length(pix_x)
     y=BrightTN(:,pixels(xx));
     p=polyfit(x,y,4);
     P(xx,:)=p(1,:);
     y1= polyval(p,x);
     plot(x,y1,Color(xx))
end

When using polyval() on these, everything fine, i get value between 0 and 1.

R=zeros(134,3);x=sigma;
R(:,1)= polyval(P(1,:),x);
R(:,2)= polyval(P(2,:),x);
R(:,3)= polyval(P(3,:),x);

If a create a matrix by manually entering same value , polyval() return bad value between -38 and 64, i don't understand why.

P2=[-1.9563e-10    8.8342e-7     -0.0015    1.0858   -296.2330;
     4.8228e-10   -2.0601e-6      0.0033   -2.2701    585.5897;
    -3.7439e-10    1.7088e-6     -0.0029    2.1705   -602.1542;];

[David Young]

Maybe the values are different. What do you see with

disp(P - P2);

?

[dpb]

No way we can tell; you don't show any variable x in the first loop and we don't have your raw data.

But, polyval is deterministic with the same inputs, so at_least_one of the inputs to it is different between the two cases.