Re: "expanding a list"

*To*: mathgroup at smc.vnet.net*Subject*: [mg57940] Re: [mg57860] "expanding a list"*From*: Ken Levasseur <klevasseur at mac.com>*Date*: Mon, 13 Jun 2005 05:51:01 -0400 (EDT)*References*: <200506100629.CAA15653@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

My first reaction was to use a pattern and rule. In[56]:= expandlistRule[j_, k_] := {{a_, b___} :> Join[{Table[a, {j}]}, (Table[#1, {k}] & ) /@ {b}]} In[57]:= Range[5] /. expandlistRule[4, 2] Out[57]= {{1, 1, 1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}} In[58]:= Range[1] /. expandlistRule[4, 2] Out[58]= {{1, 1, 1, 1}} In[59]:= Range[5] /. expandlistRule[0, 2] Out[59]= {{}, {2, 2}, {3, 3}, {4, 4}, {5, 5}} In[61]:= Range[5] /. expandlistRule[2, 0] Out[61]= {{1, 1}, {}, {}, {}, {}} On Jun 10, 2005, at 2:29 AM, Mark Coleman wrote: > Greetings, > > I'd like to construct a list as follows. Say I have a list of reals > {x1,x2,x3,...xn}, and another list of integers {r,s}. I'd like to > make a new list > > {{x1,x1,x1,...},{x2,x2,x2....},{x3,x3,x3,...},....,{xn,xn,xn,...}}, > where the first sublist is of length r, and the remaining sublists > are of length s. > > > Thanks, > > -Mark > > > > Ken Levasseur http://homepage.mac.com/klevasseur/

**References**:**"expanding a list"***From:*Mark Coleman <mark@markscoleman.com>