Ask A Scientist Mathematics Archive

Question: I am using Lotus 123 for Windows and want to calculate the 
determinant of a matrix?  Has anyone ever written a macro or can help in 
setting one up?
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No, I have never written a Lotus 1-2-3 macro for that purpose, but 
I have calculated a few determinants numerically in my day.  The simplest way 
I know of is through LU decomposition.  Suppose we want the determinant of a 
matrix X.  If we can somehow decompose the matrix into the product of two 
matrices, i.e., X = L * U, and do it in such a way that L is "lower-
triangular" (all non-zero elements on the diagonal and below) and U is "upper-
triangular" (all non-zero elements on the diagonal and above), then we can use 
L and U to get the determinant.  This whole procedure is described in detail 
in a book called: Numerical Recipes by W.H. Press, B.P. Flannery, S.A. 
Teukolsky, and W.T. Vetterling (Cambridge Press, Cambridge, 1986).  It should 
be in the library of your local university/college.  Hope this has been 
helpful. 
Topper
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