Re: How to quickly find number of non-zero elements in sparse matrix rows?

*To*: mathgroup at smc.vnet.net*Subject*: [mg56900] Re: How to quickly find number of non-zero elements in sparse matrix rows?*From*: Paul Abbott <paul at physics.uwa.edu.au>*Date*: Mon, 9 May 2005 01:46:46 -0400 (EDT)*Organization*: The University of Western Australia*References*: <d5hum0$k03$1@smc.vnet.net> <d5j5ec$qdr$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <d5j5ec$qdr$1 at smc.vnet.net>, Paul Abbott <paul at physics.uwa.edu.au> wrote: > For the full array, the following is quite reasonable: > > Most[Length /@ Split[ArrayRules[sa], #1[[1,1]]==#2[[1,1]]&]]; //Timing Chris Chiasson <chris.chiasson at gmail.com> pointed out that my code does not work if the array has all zero rows. This is easy to fix: {#[[1,1,1]],Length[#]}& /@ Split[ArrayRules[sa], #1[[1,1]]==#2[[1,1]]& ] // Most returns the row number and number of non-zero entries in sa. Cheers, Paul -- Paul Abbott Phone: +61 8 6488 2734 School of Physics, M013 Fax: +61 8 6488 1014 The University of Western Australia (CRICOS Provider No 00126G) AUSTRALIA http://physics.uwa.edu.au/~paul http://InternationalMathematicaSymposium.org/IMS2005/

**Follow-Ups**:**Re: Re: How to quickly find number of non-zero elements in sparse matrix rows?***From:*Sseziwa Mukasa <mukasa@jeol.com>