Ploting a function and its roots

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Harel Harel Shattenstein 2018-7-5

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评论： Star Strider 2018-7-5

f=@(x)x.^2-5*sin(x);
[p1,p2]=fzero(f,1,[-1,3])
fplot(f1,[-1,3])

Can I "draw" the roots p1,p2 in the same function fplot?

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Answer 1

Star Strider 2018-7-5

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The fzero function will only return one value for each initial estimate. You need to provide different initial estimates in different calls to it, if you want other roots. (For several roots, this usually requires a for loop.) Plotting the results is then straightforward.

Try this:

f=@(x)x.^2-5*sin(x);
p1 = fzero(f,1);
p2 = fzero(f,5);
fplot(f,[-1,3])
hold on
plot([p1,p2], [0 0], 'p')
hold off

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Harel Harel Shattenstein 2018-7-5

编辑：Harel Harel Shattenstein 2018-7-5

I can use fsolve too?

Star Strider 2018-7-5

Yes. However it is subject to the same initial estimate constraints, so that different initial estimates can result in different zeros and different parameter estimates, at least in my experience. The difference is that fsolve (link) finds parameters defining roots of systems of functions, and is not limited to single functions, as is fzero.

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