Help plotting interpolation ploynomial.

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Yuval
Yuval 2013-11-1
评论： Matt J 2021-3-21
Hi, I was asked to plot psi_n(x) = (x-x_0)(x-x_1)...(x-x_n) for n = 3,7,10,17 evenly distributed nodes in [-5,5] with resolution 0.01. Below is my code:
x=-5:0.01:5;
n=[3 7 10 17];
for j=1:4
node=-5;
psi=1;
while (node <= 5)
psi=psi.*(x-node);
node=node + 10/n(j);
end
subplot(2,2,j);
plot(psi)
hold on
end
Which doesn't quite yield the desired output. Or does it? In any case, it doesn't seem to match what I am getting via using Wolfram. My question is why and, of course, how may I correct it? I'd sincerely appreciate your assistance. Thanks in advance!

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回答（1 个）

Matt J
Matt J 2013-11-1
编辑：Matt J 2013-11-1
node=linspace(-5,5,n);
p=poly(node);
f=@(z) polyval(p,z);
x=-5:0.01:5;
plot(x,f(x));
  4 个评论
显示 2更早的评论
Victor McNstein
Victor McNstein 2021-3-20
Hello Matt. How does on combine your code with Yuval's initial work, for better results?
Matt J
Matt J 2021-3-21
I do not see what Yuval thought was incomplete about my code. I think my code already fulfills the entire task.

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