Why do I have an error on line 17 of the code? or there is another error

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Freddy
Freddy 2023-11-30
编辑： Torsten 2023-12-1
Ran in:
syms x
f=x.^8-7*x.^3 + 7;
d=diff(f);
fplot(f,[0 10]);
pause(1);
hold on;
lambda=1;
xo=1;
fxo=1;
x_value=[];
y_value=[];
for i=1:50
x_value=[x_value xo];
y_value=[y_value fxo];
xo=xo-lambda*d;
fxo=xo.^8-7*xo.^3+7; % Corrección aquí
plot(x_value,y_value,'*','linewidth',1);
pause(0.02)
end
Error using plot
Data must be numeric, datetime, duration, categorical, or an array convertible to double.
toc
  2 个评论
Dyuman Joshi
Dyuman Joshi 2023-11-30
xo=xo-lambda*d;
What is this line suppossed to do?
xo and lambda are numbers, but d is an expression in the symbolic variable x.
Freddy
Freddy 2023-12-1
移动：Voss 2023-12-1
I try to capture the gradient descent method and that line iterates the values until the minimum is found.

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采纳的回答

Walter Roberson
Walter Roberson 2023-12-1
syms x
f=x.^8-7*x.^3 + 7;
d=diff(f);
d is a symbolic expression in x
xo=xo-lambda*d;
That symbolic expression in x is used. Note that you are not evaluating d at the current point, so the result is going to involve the symbolic variable x, so you will not be able to convert the result to numeric form.

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