MATLAB: Find the Error – FZero Function. Constant loop.

anonymous functionsdiff()duplicate post requiring mergingfsolvefunction handlesfzeroglobalMATLAB

[EDIT: Thu May 12 22:17:54 UTC 2011 Duplicate Removed, Reformat – MKF]
Okay so I can't seem to find this last error in my program. I just get a constant loop.
My first function file for Consumers reads:
function  F = Consumer2(x)        
%f1=N
%f2=n
%f3=k
global a R K W B w r
f1= (a*W)/(R*K + W*x(1) - x(3))+(a-1)/(1-x(1));
f2= B*((a*w)/(r*x(3) + w*x(2))+((a-1)/(1-x(2))));
f3= (-a/(R*K + W*x(1) - x(3))) + B*((a*r)/(r*x(3) + w*x(2)));
F= f1^2 + f2^2 + f3^2;
end
The second function file for firm profit reads:
function F = Firm2(x)        
%F1=N
%F2=n
%F3=k
global p r w K W
F1=.6*p*(K^.3)*((x(1))^-.4)-W;
F2=.6*p*((x(3))^.3)*((x(2))^-.4)-w;
F3=.3*p*((x(3))^-.7)*((x(2))^.6)-r;
F = F1^2 + F2^2 + F3^2;
end
Finally my executable is:
global a R K W p B r w
a=2/3;
R=.1409;
K=2;
W=.8;
p=1;
B=.95;
r=.5;
w=.7;
diff=1;
diff1=0;
diff2=0;
diff3=0;
while diff>.001
NCons=fminsearch('Consumer2',[.2,.1,.5])
NFirm=fminsearch('Firm2',[.2,.1,.5])
diff1=NCons(1)-NFirm(1);
W=W-.05*diff1;
diff2=NCons(2)-NFirm(2);
w=w-.05*diff2;
diff3=NCons(3)-NFirm(3);
r=r-.05*diff3;
diff=diff1^2+diff2^2+diff3^2;
end
When I run the executable i get an infinite loop. Any help?

Best Answer

The root of the problem is that you're trying to solve for NCons = NFirm by minimizing each of these functions at each step. The minimization is failing each time, leaving huge residuals. Here is a better way to solve it. Define your functions as
function F = Consumer2(x,a,R,K,B) %f1=N %f2=n %f3=k
f1= (a*x(4))/(R*K + x(4)*x(1) - x(3))+(a-1)/(1-x(1));
f2= B*((a*x(5))/(x(6)*x(3) + x(5)*x(2))+((a-1)/(1-x(2))));
f3= (-a/(R*K + x(4)*x(1) - x(3))) + B*((a*x(6))/(x(6)*x(3) + x(5)*x(2)));
F= f1^2 + f2^2 + f3^2;
and
function F = Firm2(x,K,p)
F1=.6*p*(K^.3)*((x(1))^-.4)-x(4);
F2=.6*p*((x(3))^.3)*((x(2))^-.4)-x(5);
F3=.3*p*((x(3))^-.7)*((x(2))^.6)-x(6);
F = F1^2 + F2^2 + F3^2;
(I have replaced W, w, r by x(4), x(5), x(6)). Then run:
a=2/3; R=.1409; K=2; W=.8; p=1; B=.95; r=.5; w=.7;
residual=1; residual1=0; residual2=0; residual3=0;
f = @(x) Consumer2(x,a,R,K,B)-Firm2(x,K,p);
xsol=fsolve(f,[.2,.1,.5, W, w, r]);
The line f = @(x) ... is what Matt means by points 2 and 3.
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