Re: count the number of sub-list in a list
- To: mathgroup at smc.vnet.net
- Subject: [mg122241] Re: count the number of sub-list in a list
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Sat, 22 Oct 2011 06:06:10 -0400 (EDT)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
On 10/21/11 at 7:28 AM, hitphyopt at gmail.com (Gy Peng) wrote:
>I have a list like:
<array snipped>
>I consider each of {{*, *, *}, {*, *, *}, {*,*,*}} is one single
>element, so how could I count how many element in the whole list?
>Thank you very much!
Using data to be your array
In[17]:= Times @@ Drop[Dimensions[data], -2]
Out[17]= 16
Here, I use the fact the element you want to count is a n x m
array. So, the last two values in the list returned by
Dimensions will be the dimensions of the element. Dropping the
last two values gives the dimensions of an array of n x m
elements. So, the product is the number of those m x n elements.
Equivalently, you could compute the total number of entries at
the lowest level then divide by the number of entries in you
element, i.e.,
In[18]:= Times @@ Dimensions[data]/9
Out[18]= 16