2 while loops one after the other

Hi everyone.

I am trying to make some numerical calculations and I need two different ''while'' loops. The first ''while'' loop calculates A,B for exapmle, and the second ''while'' loop calculates C as a function of A,B.

This is the code

P.gamma = 2;

P.beta = 0.98;

Pr.R = 1/P.beta-1e-4;

tol = 1e-15;

maxit = 10000;

P.gridsize = 200;

P.min = 0;

P.max = 20;

P.grid = linspace(P.min.^0.25, P.max.^0.25, P.gridsize).^4;

P.N = 2;

P.e1 = 0.8;

P.e2 = 1.2;

P.endow = [P.e1,P.e2];

pr = zeros(P.N,P.N);

pr(1,1) = 0.5;

pr(2,1) = 0.5;

pr(1,2) = 0.5;

pr(2,2) = 0.5;

% Auxiliary matrices

P.tiledGrid = repmat(P.grid,2,1);

P.tiledEndow = repmat(P.endow',1,P.gridsize);

% Guess for a

G = 10+0.1*P.tiledGrid;

dif = 1;

it=0;

disp('solving for policy rules')

tic

% Start Loop that Iterates on Euler Equation until the fixed point is reached

while dif>tol && it<maxit

it = it+1;

% Create c_t+1

cp = zeros(P.N,P.gridsize);

for i=1:P.N

app = interp1(G(i,:),P.grid,P.tiledGrid(i,:),'linear','extrap');

app(app<0)=0;

cp(i,:) = Pr.R*P.tiledGrid(i,:)+P.tiledEndow(i,:)-app;

end

upcp = cp.^(-P.gamma); % u'(c_t+1)

Eupcp = [];

for i_p = 1:P.N

Eupcp(i_p,:) = pr(:,i_p)' * upcp;

end

upc = P.beta*Pr.R*Eupcp;

c = upc.^(-1/P.gamma);

a = (P.tiledGrid+c-P.tiledEndow)/Pr.R;

% Check for convergence

if mod(it,50) == 0

dif = max(max(abs(a-G)/(abs(a)+abs(G)+tol)));

fprintf('it = %d, dif = %.3f\n',[it,dif]);

end

G = a;

end

toc

ap(1,:) = interp1(G(1,:),P.grid,P.grid,'linear','extrap');

ap(2,:) = interp1(G(2,:),P.grid,P.grid,'linear','extrap');

ap(ap<P.min)=P.min;

c_pr(1,:) = interp1(G(1,:),c(1,:),P.grid,'linear','extrap');

c_pr(2,:) = interp1(G(2,:),c(2,:),P.grid,'linear','extrap');

u = (c_pr.^(1-P.gamma)-1)./(1-P.gamma);

% Guess for V

V = 0*P.tiledGrid;

test = 1;

iter = 0;

disp('solving for value function')

while test>tol && iter<maxit

iter = iter+1;

v_v = zeros(P.N,P.gridsize);

for i = 1:P.N

%Vp(i,:) = interp1(G(i,:),V(i,:),P.tiledGrid(i,:),'linear','extrap');

Vp(i,:) = interp1(P.grid,V(i,:),ap(i,:),'linear','extrap');

end

E_Vp = [];

for i=1:P.N

E_Vp(i,:) = pr(:,i)'*Vp;

end

V_new = u + P.beta*E_Vp;

if mod(it,100) == 0

test = max(max(abs(V-V_new)/(abs(V)+abs(V_new)+tol)));

fprintf('iter = %d, dif = %.12f\n',[iter,test])

end

V = V_new;

end

figure;

subplot(1,2,1);

hold on;

plot(P.grid,c_pr)

xlabel('Current Assets a');

ylabel('Consumption');

legend({'Low endowment','High endowment'});

%legend('High/Low endowment');

grid on;

subplot(1,2,2);

hold on;

plot(P.grid,ap-P.grid) % y-axis a_t+1, x-axis a_t

xlabel('Current Assets a')

ylabel('Savings a΄')

legend('Low endowment','High endowment');

grid on;

figure;

plot(P.grid,V_new);

xlabel('Current Assets a');

ylabel('V_{t}');

legend('Low endowment','High endowment');

title('Value Function');

grid on;

The thing is that while matlab generates a plot for V_new (calculated in the second ''while'' loop), I am not sure whether the second ''while'' loop works properly. And while in the command window i can see after how many iterations the first iterative procedure has converged, i can't see the same for the second ''while'' loop. Any idea whether the code is fine and how i can manage to see the iterations (and whether it has converged) for the second loop in the command window?

Answer 1

[Shiva Kalyan Diwakaruni]

Hi ,

In the first while loop you have used the variable name 'it' for calculating the iterations and in the second while loop you have used 'iter' for calculating the iterations and used variable 'it' in the if mod(it,100) == 0 change the variable name to 'iter' in

if mod(iter,100) == 0 and you can manage to see the iterations (and whether it has converged) for the second loop in the command window

hope it helps.