How can i use elements with equal indexes?

1 次查看（过去 30 天）
Azime Beyza Ari
Azime Beyza Ari 2022-4-10
评论： Azime Beyza Ari 2022-4-10
Hello everyone, I am working on an constraint where i will only use the elements of an matrix if their indexes are equal like;
for i=1:36
for j=1:36
if i=j
M*x(i,j)-y(j)>=0
else
end
end
end
my matrix has 36x36 dimensions so need to go from 1 to 36.
this is what i did for y ;
y(:,1)
y is 36x1 so this works for y.
i i can not use any loops or conditions i am trying to write this only in one line! if there is a little tip like
x(do something here);
that is what i need.
Hope i can make what i need clear.
Thank you in advance!

请先登录，再回答此问题。

采纳的回答

Matt J
Matt J 2022-4-10
problem.Constraints.diagcon=diag(x)*M-y>=0;

更多回答（1 个）

Torsten
Torsten 2022-4-10
编辑：Torsten 2022-4-10
Put "-M" in the matrix of inequality constraints where x_jj is addressed and "+1" where y(j) is addressed.
Then you have set the constraint
-M*x_jj + y_j <= 0
or
M*x_jj - y_j >= 0
This will result in 36 new rows in the constraint matrix A and 36 new zeros in the vector b of the right-hand side.
  3 个评论
显示 1更早的评论
Torsten
Torsten 2022-4-10
And
for i=1:36
constr(i) = M*x(i,i)-y(i) >= 0
end
does not work ?
Steven Lord
Steven Lord 2022-4-10
Ran in:
So you only want to operate on diagonal elements of x?
x = magic(4)
x = 4×4
16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1
y = [1; 2; 3; 4]
y = 4×1
1 2 3 4
result = 2*diag(x) - y
result = 4×1
31 20 9 -2
n = 3;
spotcheck = [2*x(n, n)-y(n), result(n)] % These should match
check = 1×2
9 9

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

产品


版本

R2022a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by