How can i modify this code so x can = 0
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function qw=fNR(x)
qw=zeros(100,1)
qw(2)=x
i=2
while abs(qw(i)-qw(i-1))>1e-6
qw(i+1)=qw(i)-ff1(qw(i))/fdf1(qw(i))
i=i+1
end
qw=qw(2:i-1)
[qw(end) i]
plot(qw)
end
how can i model this functio so it can take fNR(0)
fdf1
function y=fdf1(x)
y=3*x.^2-12*x+11;
end
ff1
function y=ff1(x)
y=x.^3-6*x.^2+11*x-5;
end
回答（1 个）
Image Analyst
2022-2-12
Try this:
function qw=fNR(x)
qw=zeros(100,1)
qw(2)=x
i=2
maxIterations = 1000;
loopCounter = 0;
while (abs(qw(i)-qw(i-1))>1e-6) && loopCounter < maxIterations
qw(i+1)=qw(i)-ff1(qw(i))/fdf1(qw(i))
i=i+1
loopCounter = loopCounter + 1;
end
qw=qw(2:i-1)
if isempty(qw)
message = sprintf('qw is empty')
uiwait(warndlg(message));
return;
end
[qw(end) i]
plot(qw)
end
5 个评论
Muhammad Choudhury
2022-2-12
编辑：Muhammad Choudhury
2022-2-12
DGM
2022-2-12
That's showing up because the loop never starts. Since the loop never starts, pruning the vector:
qw=qw(2:i-1);
results in a zero-length vector. Trying to index to qw(end) is the same as qw(0), which isn't a valid index.
You can at least get it to start by doing this.
i=2;
dqw = 1;
while dqw > 1e-6
qw(i+1) = qw(i)-ff1(qw(i))/fdf1(qw(i));
[qw(i) qw(i-1)]
dqw = abs(qw(i)-qw(i-1))
i = i+1;
end
Muhammad Choudhury
2022-2-12
DGM
2022-2-12
Oops. I didn't realize I was commenting on the answer instead of on the question.
Image Analyst
2022-2-13
@Muhammad Choudhury I know that was your error with the original code. Obviously you never ran my code because my code throws up an alert that the array is empty rather than your error.
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