Why do I get NaN result?

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Ludvig Hultman 2020-10-12

0
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https://ww2.mathworks.cn/matlabcentral/answers/611196-why-do-i-get-nan-result

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Hi,

When I'm using the steepest descent method I have a hard time getting the result on the x:cordinate.

In the code below, the issue arises in "gradf". Can someone help me?

n=0;            %initialize iteration counter 
eps=1;          %initialize error 
a=0.04;         %set iteration parameter 
x=[-1;-1];        %set starting value
 
%Computation loop 
while eps>0.5e-4&n<100 
    gradf=[3*x(1)^2+0.8*x(1)+2.8*x(2); 2.8*(x(1))+2.7*(x(2))^2-1.1];  %gradf(x) 
    eps=abs(gradf(1))+abs(gradf(2));                             %error 
    y=x-a*gradf;                                                 %iterate 
    x=y;                                                         %update x 
    n=n+1;                                                       %counter+1 
end 
n,x,eps,        %display end values