Re: sparse matrix question

*To*: mathgroup at smc.vnet.net*Subject*: [mg56155] Re: sparse matrix question*From*: Peter Pein <petsie at arcor.de>*Date*: Sun, 17 Apr 2005 03:06:59 -0400 (EDT)*References*: <d3lrsq$sef$1@smc.vnet.net> <200504150847.EAA11518@smc.vnet.net> <d3qh7j$odd$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Ted Sariyski wrote: > Hi, > > I have a list > l={{a,b},{c,d},{e,f}} > and a list of pointers to the non-zero columns of a > sparse matrix e.g. p={3,4,6}: > > | 0 0 a c 0 d 0 ... | > m= | | > | 0 0 b d 0 e 0 ... | > > What is the best way to do this? How can I address a column in > mathematica? > > Thanks, > Ted > > > > m = {{0, 0, 0, a, c, 0, d, 0, andsoon}, {0, 0, 0, b, d, 0, e, 0, more}}; In[2]:= m[[All,4]] Out[2]= {a, b} In[3]:= m[[All,#]]& /@ Range[Min[Length /@ m]] Out[3]= {{0, 0}, {0, 0}, {0, 0}, {a, b}, {c, d}, {0, 0}, {d, e}, {0, 0}, {andsoon, more}} -- Peter Pein Berlin

**References**:**Re: Wierd problems with Mathematica - inversion of a 12x12 matrix***From:*David Bailey <dave@Remove_Thisdbailey.co.uk>