Feature #10073: [PATCH] Implement Laplace expansion for matrix.

• Status: Closed
• Assignee: marcandre (Marc-Andre Lafortune)
• Target version: 2.2.0

[gogotanaka (Kazuki Tanaka)]

Laplace expansion has really important mathematical property.

We can handle many thing with this (determinant, cross product)

So I'm confident that this method is necessary.

But I recognize Ruby should be not for mathematician but rubyist.

Ruby doesn't need too academic method.

So If you think it is too academic you can ignore my patches.

gogo.

[gogotanaka (Kazuki Tanaka)]

For all n * n matrix m,   k <- {1, 2, ..., n}.

m.laplace_expansion(k-1, :row) == m.laplace_expansion(k-1, :column) == m.det


It is important when we think about values contains not Scalar, like that.

Matrix[[Vector[1, 0], Vector[0, 1]], [2, 3]].laplace_expansion(0, :row)
=> Vector[3, -2]

And, this patch is needed in https://bugs.ruby-lang.org/issues/10074.

gogo.

[hsbt (Hiroshi SHIBATA)]

• Category set to lib
• Assignee set to marcandre (Marc-Andre Lafortune)
• Target version set to 2.2.0

[hsbt (Hiroshi SHIBATA)]

• Status changed from Open to Assigned

[marcandre (Marc-Andre Lafortune)]

Looks good.

I'd change the interface slightly so we can call it with named parameters instead:

m.laplace_expansion(row: k-1) == m.laplace_expansion(column: k-1) == m.det

Of course, m.laplace_expansion or m.laplace_expansion(row: 0, column: 0) would raise errors.

@gogo tanaka: what do you think about this?

[gogotanaka (Kazuki Tanaka)]

@Marc-Andre Lafortune

Thank you very much for responding.

m.laplace_expansion(row: k-1) == m.laplace_expansion(column: k-1) == m.det

The interface you suggested is really make sense for me.

OK, Let me handle this.

[marcandre (Marc-Andre Lafortune)]

Just to be clear: you'd like me to wait for an updated patch, or should I make the small changes myself?

[gogotanaka (Kazuki Tanaka)]

Sorry, I should make that be clear.

OK, I'll update patch. Please wait for some time.

[gogotanaka (Kazuki Tanaka)]

• File update_news.patch update_news.patch added
• File add_test_for_laplace_expansion.patch add_test_for_laplace_expansion.patch added
• File implementing_laplace_expansion.patch implementing_laplace_expansion.patch added

@Marc-Andre Lafortune

Thank you for your great proposal.

[marcandre (Marc-Andre Lafortune)]

• Status changed from Assigned to Closed

Great, thanks for the updated patch.