# [plt-scheme] Matrix Determinants

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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