Re: Dynamic iterators in Do loop

*To*: mathgroup at smc.vnet.net*Subject*: [mg66299] Re: Dynamic iterators in Do loop*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Mon, 8 May 2006 00:46:46 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 5/6/06 at 11:50 PM, iwillfail at gmail.com (sai) wrote: >I have an (n,n) matrix. I want to define an (m,m) matrix [m<n] whose >elements are defined from the (n,n) matrix. The value of n and m >changes from problem to problem. How can i do this in mathematica? There are a number of ways to accomplish what you want. Which is best would depend on precisely what you want to do. For example, the upper m X m sub-matrix can be extracted from the n X n matrix (a) as follows: Take[Take[#,m]&/@a,m] Once the sub-matrix is obtained Map can be used to Map any arbitrary function to each element of the matrix. For example, In[30]:= n=4; m=3; a=Table[10 i+j,{i,n},{j,n}]; b=Take[Take[#,m]&/@a,m]; Map[Total[IntegerDigits@#]&,b,{2}] Out[34]= {{2, 3, 4}, {3, 4, 5}, {4, 5, 6}} -- To reply via email subtract one hundred and four