checking script's output

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milad babaei
milad babaei am 4 Aug. 2011
Hi all,
i've uesd those two code in a script to fit a polynomial on my data.the evauation output(command: polyval2(P,x,y))tells us,it's a good fit but when i made the equation with coefficients which produced by P = polyfitweighted2(x,y,z,9,w)i couldn't reach to that evaluated point( tested at specific point)which is produced by the coomand polyval2(P,x,y).i would like to ask somebody plz help me to find how could i get to a evaluated point through equation at a point???
link for two functions :
http://www.mathworks.com/matlabcentral/fileexchange/13719-2d-weighted-polynomial-fitting-and-evaluation
my script:
BoverH=1:8;
phi=0:10:30;
mydata = [ 1 1.02 1.11 1.21 1.3 1.4 1.59 1.78; ...
1 1.11 1.35 1.62 1.95 2.33 3.34 4.77; ...
1.01 1.39 2.12 3.29 5.17 8.29 22 61; ...
1.13 2.5 6.36 17.5 50 150 1400 14800];
h=log(mydata);
y=phi;
x=BoverH;
z=h;
w=ones(size(z));
P = polyfitweighted2(x,y,z,9,w);
[c, hh]=contour(x,y,z); clabel(c,hh), colorbar
title('data')
figure
[c, hh]=contour(x,y,polyval2(P,x,y)); clabel(c,hh), colorbar
title('equal weight')
  1 Kommentar
milad babaei
milad babaei am 4 Aug. 2011
According to the script and the function P = polyfitweighted2(x,y,z,9,w) and command polyval2(P,x,y),we able to make equation with coeff.which are made by function P.and evaluted the equation at a specific point like(X1,Y1).but my problem is :i couldn't get that equation to check and evaluate at the point which this command polyval2(P,x,y) gives me on output.i would like to ask you help me on making z equation .for example i reached to the equation after running the script and producing coefficients :
z=log(h): -0.0026-.0009(x^3)+0.0033(x^5)-0.0017(x^6)+0.003(x^7)-0.0004(x^6*y)+0.0004(x^4*y^3)-0.0002(x^3*y^4)+0.0001(x^2*y^5)
x=(B/H),y=phi..........at this (x=4 and y=0)point for evaluating fitted equation and checking the result of polyval2(P,x,y).it gives me z=log(h)=1.271....which h=e^1.271=3.56 but according to polyval2(P,x,y) output for this point gives us e^0.1936 =1.21??????
so my question is :is that equation which i have made with those coefficients correct???and why i couldnt get those evaluated number through the equation?also whats the W on a
> coefficients definition(wZ) on a script definition??

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