Determinant of integer matrices

2 次查看（过去 30 天）
Rudolf Fruehwirth
Rudolf Fruehwirth 2021-4-23
评论： Matt J 2021-4-23
Is there a version of the det function in R2020a that alway gives determinant 0 for small singular integer matrices?
  4 个评论
显示 2更早的评论
Rudolf Fruehwirth
Rudolf Fruehwirth 2021-4-23
And it should work without prior knowledge whether the entries are integer or not. Probably asking too much...
Matt J
Matt J 2021-4-23
And it should work without prior knowledge whether the entries are integer or not. Probably asking too much...
No, one of hte answers below meets that requirement.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（2 个）

Matt J
Matt J 2021-4-23
编辑：Matt J 2021-4-23
Since you know A is an integer matrix, can't you just do,
d=round(det(A));
  3 个评论
显示 1更早的评论
Matt J
Matt J 2021-4-23
OK. Well, maybe the A(i,j) are supposed to be "small" in mangitude as well...
John D'Errico
John D'Errico 2021-4-23
Ran in:
A = randi(3,29,30);
A(end+1,:) = round(rand(1,29)*2-1)*A
A = 30×30
2 3 2 3 2 1 1 2 2 2 1 1 1 3 3 2 3 2 1 3 3 1 2 2 1 1 1 3 3 2 1 3 3 2 2 3 1 1 2 1 1 2 3 3 2 2 2 2 2 1 1 1 2 2 2 2 1 1 1 1 1 2 3 1 1 1 3 3 1 1 1 2 2 1 1 3 2 3 2 1 3 3 2 1 1 2 3 1 2 3 3 1 2 1 2 3 3 1 1 1 1 1 1 1 1 2 2 2 1 2 3 3 1 2 2 1 2 3 1 2 3 2 2 1 1 1 3 1 2 1 2 1 2 1 2 2 1 3 2 3 1 3 3 3 3 2 2 3 3 1 1 3 1 3 1 3 1 1 1 2 2 2 2 1 1 3 1 2 2 3 3 1 2 2 1 1 1 1 1 3 3 1 1 3 3 3 3 1 1 1 1 3 1 3 1 1 3 2 1 3 1 3 2 3 2 1 2 1 3 3 3 2 3 3 3 1 3 1 1 1 3 2 3 2 3 3 3 1 3 1 3 2 2 1 3 3 1 3 2 3 2 3 3 3 3 1 2 2 1 3 1 2 3 3 2 1 1 1 3 1 2 3 3 3 3 1 3 3 2 1 3 2 1 2 2 3 1 1 3 2 3 1 2 3 3 1 3 1 1 3 1 2 1 2 3 2 2 3 1 2
rank(A)
ans = 29
det(A)
ans = 0.5894
round(det(A))
ans = 1
Ok, I guess it works, some of the time. But not this one.
If the matrix is truly tiny, well yes.
A = magic(4)
A = 4×4
16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1
rank(A)
ans = 3
det(A)
ans = 5.1337e-13
round(det(A))
ans = 0
But you really cannot trust that rounding the determinant will work unless things are truly tiny.

请先登录，再进行评论。

Matt J
Matt J 2021-4-23
编辑：Matt J 2021-4-23
Ran in:
This might work,
A = randi(10000,[9,10]);
A(end+1,:) = randi(10,[1,9])*A;
determinant=double(det(sym(A)))
determinant = 0

类别

在 Help Center 和 File Exchange 中查找有关 Creating and Concatenating Matrices 的更多信息

标签

产品


版本

R2020a

Community Treasure Hunt

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

Start Hunting!

Translated by