Re: Transforming a list
- To: mathgroup at smc.vnet.net
- Subject: [mg103149] Re: Transforming a list
- From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
- Date: Wed, 9 Sep 2009 04:44:20 -0400 (EDT)
- References: <h859pi$ps0$1@smc.vnet.net>
To get rid of the zeros you could use DeleteCases:
In[113]:= DeleteCases[{{c, d, e, f, g, 0}, {e, f, g, 0, 0, 0}, {g, 0,
0, 0, 0, 0}}, 0, Infinity]
Out[113]= {{c, d, e, f, g}, {e, f, g}, {g}}
The following would do the whole trick:
Cases[lst, x_ /; Length[x] >= #][[All, #]] & /@
Range[Max[Length /@ lst]]
as would the utterly incomprehensible version below (why do it simple
if you could make life difficult and interesting?)
Reap[
NestWhile[
(
Sow[Cases[#, x_ /; x != {}][[All, 1]]];
Cases[#, x_ /; x != {}][[All, 2 ;; -1]]
) &,
lst,
Flatten[#] != {} &
]
][[2, 1]]
Cheers -- Sjoerd
On Sep 8, 11:57 am, Don <don... at comcast.net> wrote:
> I am given: lst = {{c, e, g}, {d, f}, {e, g}, {f}, {g}, {}}
>
> I want to form a list of sublists where the first sublist consists of the=
first elements
> from each sublist of lst, the second sublist the second elements from eac=
h of the sublists of lst etc.
>
> The final outcome should be:
> {{c, d, e, f, g}, {e, f, g}, {g}}
>
> I can do this by first padding the sublists of lst (to make them the same=
length)and then using Transpose. But how to get rid of the trailings 0's?
>
> For example:
>
> newLst = Map[PadRight[#, Length[lst[[1]]]] &, lst]
>
> Transpose[newLst]
>
> which produces:
>
> {{c, d, e, f, g, 0}, {e, f, g, 0, 0, 0}, {g, 0, 0, 0, 0, 0}}
>
> Is there a better way to end up with
>
> {{c, d, e, f, g}, {e, f, g}, {g}}
>
> Thank you.