MATLAB: Contour plot issue

contourMATLAB

Hello,
I am sorry to pester you all again but I can't get my code to work. Here is what I have so far:-
clear all % clears all previous data
s = load('domain\data.txt');
% loads in data file
% s(:,1) data number
% s(:,2) x variables
% s(:,3) y variables
x = s(:,2);
y = s(:,3);
a = 9.5:1/100:10.49;
b = 4.5:1/100:5.49;
chi2 = [ ];
c = 0;
for n = 1:100;
    for m = 1:100;
        a_pred = a(:,n);
        b_pred = b(:,m);
        c = c+1;
        y_pred = a_pred + b_pred.* x;
        chi2(c,:) = sum((y-y_pred).^2);  
    end
end
deltachi = chi2 – min(chi2);
contour(a,b,deltachi);
about the data of s
size(x)
ans =
        1000           1
and
size(y)
ans =
        1000           1
At the moment I cannot complete a successful contour plot as both chi2 and deltachi are just strings and not arrays. Can anyone see where I am going wrong please?

Best Answer

Since y and y_pred are vectors, sum((y-y_pred).^2) is going to be a scalar, so chi2(c,:) is going to be storing a single value. Your chi2 array is going to be a vector of length max n times max m, 100 times 100. Perhaps you want to reshape it to max m by max n using reshape() and then contour that? Or easier yet, just assign to chi2(m,n) and skip using c.
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