Re: Assigning elements to a matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg47381] Re: Assigning elements to a matrix*From*: "Gareth J. Russell" <gjr2008 at columbia.edu>*Date*: Wed, 7 Apr 2004 03:16:42 -0400 (EDT)*Organization*: Columbia University*References*: <c4u3ko$9lq$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In <c4u3ko$9lq$1 at smc.vnet.net> Mark Coleman wrote: > Greetings, > > I need to create a series of n x n matrices, in both conventional and > sparse matrix formats. I have a (large) table of lists, where each > list is of the form: > > {i,j,value}, where {i,j} are the row-column indices and value is the > corresponding numerical value, i.e., m[[i,j]]=value. > > Using this data I need to create an n x n matrix where all the values > except those specified in my list are 0. I would also like to create a > similar matrix, this time using Mathematica's built-in SpareMatrix > format. > > Can anyone suggest a way to do this? > > Thanks, > > -mark Mark, Have you looked at the documentation for SparseArray? If you convert each list from {i,j,value} to {{i,j}->value} and send the resulting table to SparseArray, you've done it. Normal[mySparseArray] give you the full array equivalent. It's all in the Help Browser... Gareth Russell Columbia University