matrix operations -- shared data vs copied

*To*: mathgroup at smc.vnet.net*Subject*: [mg65917] matrix operations -- shared data vs copied*From*: robert.dodier at gmail.com*Date*: Sun, 23 Apr 2006 06:17:26 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hello, I'm trying to get a handle on what Mathematica does with some matrix operations. I wasn't able to figure it out by web or newsgroups search so maybe you can help. Suppose A is a matrix. Consider these operations. (1) B = A (2) myfunction[A] (3) B = (some way of extracting column 1 of A) (4) B = (some way of pasting A onto another matrix) The question of interest is whether modifying elements of A also modify B after operations (1), (3), and (4), and whether modifications of the formal argument within myfunction also modify the actual argument (namely A). In some math languages, B = A and myfunction[A] actually create copies of A, likewise row/column extraction and pasting matrices together. But that's not the only way to do it; I'm trying to figure out where Mathematica stands on this point. Thanks for any pointers or other information. Robert Dodier

**Follow-Ups**:**Re: matrix operations -- shared data vs copied***From:*Murray Eisenberg <murray@math.umass.edu>

**Re: matrix operations -- shared data vs copied***From:*"Szabolcs Horvát" <szhorvat@gmail.com>