[plt-scheme] Matrix Determinants

From: John Clements (clements at brinckerhoff.org)
Date: Fri Mar 28 00:47:50 EDT 2008

On Mar 27, 2008, at 9:25 PM, Henk Boom wrote:

> So, when I get bored doing math assignments, I write short programs to
> double-check my answers. It's somewhat of a bad habit actually, as it
> often ends up taking long enough that I don't have enough time to
> finish the assignment...
> Anyways, during my last assignment I came up with the following for
> taking matrix determinants and multiplying matrices. Matrices are
> lists of rows, rows are lists of numbers, all rows of a matrix are the
> same length. I wasn't really worrying about numerical error, since the
> matrices I gave it consisted of exact numbers. I'm pretty happy with
> how simple matrix-mult is ((apply map list m) is neat!), but taking
> the determinant of a matrix proved messy. I add multiples of the first
> row to the rest to zero out the rest of the first column, so I only
> need to do ~n recursive calls. It gets messy when I need to deal with
> the case that the first row has a zero as the first element, swapping
> list elements is tricky!
> Can anyone come up with a simple matrix determinant implementation?

Wikipedia suggests gaussian elimination...

John Clements

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