Re: Select[ ] Woes

*To*: mathgroup at smc.vnet.net*Subject*: [mg83150] Re: [mg83126] Select[ ] Woes*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Tue, 13 Nov 2007 03:36:54 -0500 (EST)*References*: <200711121013.FAA11004@smc.vnet.net>

On 12 Nov 2007, at 19:13, Bruce Colletti wrote: > Re 6.0.1 under WinXP. > > What's wrong with the Select statement? x is clearly a list of > positive rationals, yet none are returned. The fragment is > extracted from larger code. > > Thankx. > > Bruce > > ... > Print@x; > Print@Select[x, # > 0 &]; > ... > > {20400/12,25200/9,12000/6} > > {} > It seems clear that your list x is not a list of numbers, since in Mathematica you can't get an output like 12000/6 but instead you will always get: 12000/6 2000 This suggests that the objects at level 2 in x are not numbers, perhaps they are strings or things like HoldForm[12000/6]. In the latter case you could use: Cases[x, z_ /; z > 0, Infinity] Of course this won't work if the "numbers" are really strings. Andrzej Kozlowski

**References**:**Select[ ] Woes***From:*Bruce Colletti <vze269bv@verizon.net>