Colinear Points

[Han]

(12-25-2013 06:56 PM)Terje Vallestad Wrote:  

(12-25-2013 05:33 PM)Han Wrote:  Thanks for sharing! Quick question, though: Why check if 1/det(...) produces an error, as opposed to simply checking if det(...) is non-zero?

I'm probably a glass half empty man rather than half full...... :-)

However, I needed a trigger/trap and ISERR was the first one I found in the manual. Being new to programming PPL I did not look further. Would it in your opinion be a benefit to look for a positive rather than a negative in this instance?

Thanks, Terje

IFERR would be a perfectly fine solution if the only error produced from 1/det(...) is a division by zero error. However, there are other ways det(...) could produce an error (non-square matrix when the user accidentally creates more entries than necessary). So an error having nothing to do with colinearity would incorrectly result in the wrong conclusion of "colinear." To make the program exit gracefully when an error occurs, you may want to test the dimensions of the matrix prior to executing det(...).