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<div class="moz-cite-prefix">Hello,<br>
<br>
Le 15/10/2018 à 20:39, rsherry8 a écrit :<br>
</div>
<blockquote cite="mid:5BC4DEF8.7040508@comcast.net" type="cite">I am
trying to solve a system of two non-linear equations using fsolve.
I define the following two functions:
<br>
<br>
function z=g1(x,y)
<br>
z = x^2 + y^2
<br>
endfunction
<br>
<br>
function z=g2(x,y)
<br>
z = x^4 + y^4 - 20
<br>
endfunction
<br>
<br>
When I type something like: g2(2,2)
<br>
I get 12 which is right.
<br>
<br>
I then run the following command:
<br>
[xres]=fsolve([0,0],g1,g2);
<br>
</blockquote>
<br>
If it is provided, g2() must be the jacobian of g1(): it must
compute and evaluate the partial derivatives of g1(), with respect
to x and to y.<br>
That's definitely not the case with your g2(). It should rather
return something like [2*x 2*y].<br>
<br>
For what you likely want to do, here are two examples (extracted
from a document of mine in french, sorry):<br>
<img src="cid:part1.81482709.0457B423@free.fr" alt="" height="268"
width="545"><br>
<br>
Actually, the fsolve() page is rather poor : both given examples are
about a single variable.<br>
<a class="moz-txt-link-freetext" href="https://help.scilab.org/docs/6.0.1/en_US/fsolve.html">https://help.scilab.org/docs/6.0.1/en_US/fsolve.html</a><br>
<br>
fsolve() is a key function. We should improve its help page.<br>
<br>
HTH<br>
Samuel<br>
<br>
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