Re: Transforming/expanding a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg128017] Re: Transforming/expanding a list*From*: Dana DeLouis <dana01 at me.com>*Date*: Sun, 9 Sep 2012 05:09:26 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

> real numbers, separating some number of Strings Hi. If it's really just any String, perhaps another idea: v={1,2,"Null", 3,"Null2", "Null3",4,5,"Null4",6}; FoldList[If[StringQ[#2],#1,#2]&, First[v], Rest[v]] {1,2,2,3,3,3,4,5,5,6} = = = = = = = = = = HTH :>) Dana DeLouis Mac & Mathematica 8 = = = = = = = = = = On Thursday, September 6, 2012 4:15:28 AM UTC-4, Mark Coleman wrote: > I'm working on some Mathematica code that will help transform a large set of lists drawn from my company's legacy database systems. A typical row of the raw data looks like > > {x1,NULL,NULL,x2,NULL,NULL,NULL,NULL,x3,NULL,NULL,x4,x5,NULL} ... > > The lists are sequences of real numbers, separating some some number of Strings which for convenicence sake we call "NULL" (as opposed to a proper Mathematica Null). The goal is to create a new list where each NULL is replaced by the real number that most recently proceeds it (note that any number of NULLs may occur before or after any real values). I would like the code to return > > {x1,x1,x1,x2,x2,x2,x2,x2,x3,x3,x3,x4,x5,x5} > > > Thanks > Mark