# How to use options in fsolve

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Federico MegaMan on 14 Nov 2019
Commented: Matt J on 14 Nov 2019
Hello,
I'm trying to use the options in fsolve but i didn't understand how i can do...
I know that i have to do fsolve(@(x) myfunz,x0,options) but I don't know what i have to write, option=..?
This is my code:
j=0;
xsol=zeros(13,28);
T21=zeros(1,28);
for t=0:0.1:2.7
j=j+1;
T21(j)=0.333*cos(t)-0.245;
jT21=T21(j);
%jT21=0;
jT22=pi/2;%87°
jr23=3.1623;
jT23=4.391248;%248.5°
jT31=0;%0.226;%13°
jr32=3.1623;
jT32=1.8919369;%106°
jT33=1.5*pi;
jT11=1.106538;%62
jT12=0;
jT13=0;%01.5*pi+1.517
jT14=0;%0.226;
jT15=5.176646;%316°
for k=1:numel(T21)
x0=[jT11,jT12,jT13,jT14,jT15,jT22,jT23,jr23,jT31,jT32,jT33,jr32,jT21];
xsol=fsolve(@(x) funzz(x), [kT11,kT12,kT13,kT14,kT15,kT22,kT23,kr23,kT31,kT32,kT33,kr32,jT21]);
kT11=jxsol(1);
kT12=jxsol(2);
kT13=jxsol(3);
kT14=jxsol(4);
kT15=jxsol(5);
kT22=jxsol(6);
kT23=jxsol(7);
kr23=jxsol(8);
kT31=jxsol(9);
kT32=jxsol(10);
kT33=jxsol(11);
kr32=jxsol(12);
end
end
function F=funzz(x)
T11=x(1);
T12=x(2);
T13=x(3);
T14=x(4);
T15=x(5);
T22=x(6);
T23=x(7);
r23=x(8);
T31=x(9);
T32=x(10);
T33=x(11);
r32=x(12);
T21=x(13);
F(1)=(5^(0.5))*cos(T11)+cos(T12)+4*cos(T13)+cos(T14)+(5^(0.5))*cos(T15)-8;
F(2)=(5^(0.5))*sin(T11)+sin(T12)+4*sin(T13)+sin(T14)+(5^(0.5))*sin(T15);
F(3)=cos(T21)+3*cos(T22)+r23*cos(T23);
F(4)=sin(T21)+3*sin(T22)+r23*sin(T23);
F(5)=cos(T31)+r32*cos(T32)+3*cos(T33);
F(6)=sin(T31)+r32*sin(T32)+3*sin(T33);
F(7)=T12-T21;
F(8)=T31-T14;
F(9)=T13+T22-pi/2;
F(10)=T33-T22-pi;
F(11)=r23-(1+9+6*sin(T12-T13))^(0.5);
F(12)=r32-(1+9+6*cos(T14-T33))^(0.5);
end
But when I run it, it says:
Equation solved, fsolve stalled.
fsolve stopped because the relative size of the current step is less than the
default value of the step size tolerance and the vector of function values
is near zero as measured by the default value of the function tolerance.
<stopping criteria details>
Warning: Trust-region-dogleg algorithm of FSOLVE cannot handle non-square systems; using Levenberg-Marquardt
> In fsolve (line 310)
I saw that Levenberg-Marquardt is linked to options(is it right?), but i didn't understand how i can do.
Another thing, how can i make xsol a xsol(k)? Because matlab give me error if i put it.

Matt J on 14 Nov 2019
Edited: Matt J on 14 Nov 2019
I know that i have to do fsolve(@(x) myfunz,x0,options)
I don't think so. The exit message says "Equation solved".
Another thing, how can i make xsol a xsol(k)?
for k=1:numel(T21)
xsol(:,k)=fsolve(@(x) funzz(x), [kT11,kT12,kT13,kT14,kT15,kT22,kT23,kr23,kT31,kT32,kT33,kr32,jT21]);
end

Matt J on 14 Nov 2019
By doing something in the loop that makes them changes with k...? Currently, nothing is done with them.
Federico MegaMan on 14 Nov 2019
I did it putting jxsol=xsol(:,k), and after T11=jxsol(1), T12=jxsol(2), ecc... I did it to changes their value every iteration.
Matt J on 14 Nov 2019
Perhaps you meant to write