contour plot issue

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?

Answer 1

[Walter Roberson]

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.

[Dominic Lawson]

Thanks very much for the help. It is much appreciated.