Question

我有代码，我尝试将x作为约束但是当我运行时我总是得到一个错误，表示未定义的函数或变量'x'。下面是代码，我如何得到z值的总和？

clc;
clear;

%sum sum sum sum(fik*djq*xij*xkq)
%i,k= facilities
%j,q= location
%f(i,k)= flow between facilities i and k
%d(j,q)= distance between locations j and q
%xij = 1 if facility i is assigned to location j and if otherwise, xij = 0


% Flow matrix: flow assigning facility i (column) to facility k (row)

f = [0 5 7 9;
     5 0 4 6;
     7 4 0 3;
     9 6 3 0];

%Distance matrix: distance assigning location j (column) to location q (row)

d = [0 6 8 9;
     6 0 5 1;
     8 5 0 2;
     9 1 2 0];

z= 0;
nf= 4;%no of facilities
nd= 4;%no of locations 

for i=1:nf 
    for j=1:nf 
        for k=1:nd 
            for q=1:nd 
                z = min('z','sum(sum(f(i,k)*d(j,q)*x(i,j)*x(k,q)))');
                %if x(i,j)==1;
                %else x(k,q)==0;
            end
        end
    end
end

%Constraints 
%x as binary 0 1, 
%x(i,j) = 1 if facility i is assigned to location j 0r otherwise, x(i,j) = 0

Constraints.constr1 = (x(i,j))==1;

%The first set of constraints requires that each facility gets exactly one 
%location, that is for each facility, the sum of the location values 
%corresponding to that facility is exactly one

Constraints.constr2 = sum(x,2) == 1;

%The second set of constraints are inequalities. These constraints specify 
%that each office has no more than one facility in it.

Constraints.constr3 = sum(x,1) == 1;

disp (z);

我的代码是错误的约束吗？

Answer 1

在附带的代码中，正如我所看到的，您使用矩阵x 4次。第一个用途是在for循环中，其他3个用途是循环之后的单行。

首先，我怀疑你以错误的方式使用了函数min（）。因为参数不应该是字符。删除＆＃39;＆＃39;并使用以下行：

z = min(z,sum(sum(f(i,k)*d(j,q)*x(i,j)*x(k,q))));

现在，回答你的问题，你还没有告诉矩阵x的内容是什么，所以代码不知道存储的值是什么，例如x（1,1）或x（2， 3）。

因此，预计会抛出错误。

我如何写约束和z值的总和？

1 个答案: