Re: Transforming a list
- To: mathgroup at smc.vnet.net
- Subject: [mg103159] Re: Transforming a list
- From: pfalloon <pfalloon at gmail.com>
- Date: Wed, 9 Sep 2009 04:46:10 -0400 (EDT)
- References: <h859pi$ps0$1@smc.vnet.net>
On Sep 8, 7:57 pm, 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.
What about:
Flatten /@ Transpose[PadRight[#, Max[Length/@lst], {{}}] & /@ lst]
I've padded with empty lists (which may be safer if your original list
can contain 0's), and then Flatten'ed the Transpose which removes the
empty lists.
Cheers,
Peter.