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From: Szabolcs Horvát on 26 Jul 2010 07:17
On 2010.07.25. 8:00, Michael Stern wrote:
> If one has an irregularly nested list like
>
> {{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}}, {{1, 2, 9}, {{1, 2, 13}, {4, 5, 6}}}},
>
> How might one most easily transform this into a list of uniform Depth 2 ( {{1,2,3},{1,2,4},{1,2,3,4},{1,2,3,8},{1,2,9},{1,2,13},{4,5,6}} ) ?
>


Hi MathGroup,

Here's a little trick to do this in a single step:

d = {{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}}, {{1, 2, 9},
{{1, 2, 13}, {4, 5, 6}}}}

Level[d, {-2}]

Just use the leaves of the tree as reference when taking the items, not
the root. That is, use a negative value in the level specification.

Cheers,
Szabolcs

From: Vince Virgilio on 26 Jul 2010 06:54
On Jul 25, 2:00 am, Michael Stern <nycst...(a)gmail.com> wrote:
> If one has an irregularly nested list like
>
> {{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}}, {{1, 2, 9}, {{1, 2, 13}, {4, 5, 6}}}},
>
> How might one most easily transform this into a list of uniform Depth 2 ( {{1,2,3},{1,2,4},{1,2,3,4},{1,2,3,8},{1,2,9},{1,2,13},{4,5,6}} ) ?
>
> Thanks in advance,
>
> Michael

Michael,

Use Level.

In[1]:=
irreg={{1,2,3},{1,2,4},{{1,2,3,4},{1,2,3,8}},{{1,2,9},{{1,2,13},
{4,5,6}}}};
soln={{1,2,3},{1,2,4},{1,2,3,4},{1,2,3,8},{1,2,9},{1,2,13},{4,5,6}};
uni=Level[irreg,{-2}];
uni==soln

Out[4]= True


Vince Virgilio

From: Peter Breitfeld on 26 Jul 2010 07:18
Michael Stern wrote:

> If one has an irregularly nested list like
>
> {{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}}, {{1, 2, 9}, {{1,
> 2, 13}, {4, 5, 6}}}},
>
> How might one most easily transform this into a list of uniform Depth
> 2 ( {{1,2,3},{1,2,4},{1,2,3,4},{1,2,3,8},{1,2,9},{1,2,13},{4,5,6}} ) ?
>
> Thanks in advance,
>
> Michael
>

One possibility is to extract the list of vectors like this

ll={{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}},
{{1, 2, 9}, {{1, 2, 13}, {4, 5, 6}}}}

uniform=Cases[ll,_?VectorQ, Infinity]

Out={{1, 2, 3}, {1, 2, 4}, {1, 2, 3, 4}, {1, 2, 3, 8}, {1, 2, 9},
{1, 2, 13}, {4, 5, 6}}

--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de

From: Michael Stern on 31 Jul 2010 02:42
Thanks to everybody who responded; there were many excellent answers. This
one is the most jaw-dropping; even reading the documentation for Level[] I
would not have realized this would work.

Michael


On Jul 26, 2010, at 6:38 AM, Szabolcs Horv=E1t wrote:

> On 2010.07.25. 8:00, Michael Stern wrote:
>> If one has an irregularly nested list like
>>
>> {{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}}, {{1, 2, 9}, {{1, 2, 13}, {4, 5, 6}}}},
>>
>> How might one most easily transform this into a list of uniform Depth 2 ( {{1,2,3},{1,2,4},{1,2,3,4},{1,2,3,8},{1,2,9},{1,2,13},{4,5,6}} ) ?
>>
>
>
> Hi MathGroup,
>
> Here's a little trick to do this in a single step:
>
> d == {{1, 2, 3}, {1, 2, 4}, {{1, 2, 3, 4}, {1, 2, 3, 8}}, {{1, 2, 9},
> {{1, 2, 13}, {4, 5, 6}}}}
>
> Level[d, {-2}]
>
> Just use the leaves of the tree as reference when taking the items, not
> the root. That is, use a negative value in the level specification.
>
> Cheers,
> Szabolcs
>

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