How to change two variables in one loop?

Question

Ani Asoyan 2020-7-13

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https://ww2.mathworks.cn/matlabcentral/answers/564431-how-to-change-two-variables-in-one-loop

评论： Ani Asoyan 2020-7-14

Hi... I have something like this..

d(1)=0.3
a(1)=0.5
for i=1:5
    /some code/
     a(i+1)=a(i)-0.5*p
    d(i+1)=d(i)-0.3*p+0.5*N
end

p and N are parameters,, and I want to change a and d variables in this loop simultaneously.. how can I do that? Thank you .

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Answer 1

the cyclist 2020-7-13

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https://ww2.mathworks.cn/matlabcentral/answers/564431-how-to-change-two-variables-in-one-loop#answer_465263

编辑：the cyclist 2020-7-13

There are many things about your question that I don't fully understand. The least important is whether you meant the loop to go over k rather than i. If not, then I don't understand how i is supposed to be used.

Most importantly, I don't really understand what you mean by "simultaneously" here. Do you mean that you want to somehow execute

a(k+1)=a(k)-0.5*p

and

d(k+1)=d(k)-0.3*p+0.5*N

in a single line of code?

Why? These two lines of code do not affect each, and could be executed in either order, with same result.

You could define a function that returns a and d "simultaeously", but I'm not sure of the point of that.

Maybe I just don't fully understand your question.

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Ani Asoyan 2020-7-14

sorry for the late reply.. here's the full code.

clc
x=[0.5 , 1]
x_e=[0.5, 1]
N=[0.5, 1]
[mmm,nnn,ppp] = ndgrid(x,x_e,N);
Z = [mmm(:),nnn(:),ppp(:)];
d(1)=0.1
a(1)=0.5
for k=1:3
    
 b=1.2; c=1.5; e=1.2; l=2;
u_g = @(x, x_e, N)(-0.5*a.*x.^2+b*(x-x_e)-c*(N.^l)+e*u_p(x,x_e,N,d(k)));
g=(u_g( Z(:,1), Z(:,3), Z(:,2) ).');
p=(u_p(Z(:,1), Z(:,3), Z(:,2), d(k)).'); 
gp=reshape(g,[numel(x)*numel(N),numel(x_e)]).' ;
pp=reshape(p, [numel(x)*numel(N),numel(x_e)]).' ;
num2strcell = @(m) arrayfun(@num2str, m, 'UniformOutput', false);  
payoffs=strcat(num2strcell(gp), num2strcell(pp))
n=numel(x)*numel(N);
m=numel(x_e);
for i=1:n
A(i)=max(pp(:,i));
attainedA=(max(pp, [] ,1)==pp);
end
for j=1:m
 B(j)=max(gp(j,:));
 attainedB=( max(gp,[],2)==gp );
end
result = payoffs(attainedA & attainedB)
gov=gp(attainedA & attainedB)
pub=pp(attainedA & attainedB)
mnpg=[mmm(:), nnn(:), ppp(:), g(:)];
resval=mnpg(ismember(mnpg(:,4),gov),1:3)
 
pival=resval(1)
Nval=resval(2)
 
d(k+1)=d(k)-0.2*pival+3*Nval
a(k+1)=a(k)-0.5*pival
  end

when I run it, it gives me this error..

Error using reshape
To RESHAPE the number of elements must not change.
Error in dynamic (line 21)
gp=reshape(g,[numel(x)*numel(N),numel(x_e)]).' ;

what can I do to make g remain the same

the cyclist 2020-7-14

编辑：the cyclist 2020-7-14

When I turn that code, I get a different error. When MATLAB calls the line

g=(u_g( Z(:,1), Z(:,3), Z(:,2) ).');

I get the error

Unrecognized function or variable 'u_p'.

because

u_g = @(x, x_e, N)(-0.5*a.*x.^2+b*(x-x_e)-c*(N.^l)+e*u_p(x,x_e,N,d(k)));

and u_p is not defined in your code.

Ani Asoyan 2020-7-14

yeah sorry because there's a function called u_p ,,,here's its code

function u=u_p(x,x_e,N,d)
d=0.7-0.6*x+0.4*N
u = -(x-x_e).^2+N.*d;
end

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How to change two variables in one loop?

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