Transforming/expanding a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg127970] Transforming/expanding a list*From*: Mark Coleman <markspcoleman at gmail.com>*Date*: Thu, 6 Sep 2012 04:14:14 -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

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

**Follow-Ups**:**Re: Transforming/expanding a list***From:*Andrzej Kozlowski <akozlowski@gmail.com>

**Re: Transforming/expanding a list***From:*Bob Hanlon <hanlonr357@gmail.com>

**Re: Transforming/expanding a list***From:*Adriano Pascoletti <adriano.pascoletti@uniud.it>