[Date Index]
[Thread Index]
[Author Index]
Re: Count using pattern on two different matrices
*To*: mathgroup at smc.vnet.net
*Subject*: [mg57092] Re: Count using pattern on two different matrices
*From*: Bill Rowe <readnewsciv at earthlink.net>
*Date*: Sun, 15 May 2005 03:03:46 -0400 (EDT)
*Sender*: owner-wri-mathgroup at wolfram.com
On 5/14/05 at 4:58 AM, leenewm at umich.edu (Lee Newman) wrote:
>I have two matrices with an equal number of rows, but not
>necessarily columns, for example:
>L1= {{True,False},{False, True},{False, False}, etc.....} ; L2=
>{{True,False,False},{True, True,True},{False, True,False},
>etc.....} ;
>I would like to compute a count of the number of rows in which one
>of the columns of L1 meets some criterion, and one of the columns
>of L2 meets some criterion, i.e. If L1[[row,2 ]]==False and
>L2[[row,3]]==True then this row contributes 1 to the count.
>I suspect that there is an elegant way to do this, perhaps using
>Count[] and MapThread, but I can't figure it out other than
>resorting to a rather clumsy For or Do loop that would check line
>by line and maintain a counter.
>Any help would be appreciated, Lee
One way to accomplish what you want would be
In[1]:=
L1 = {{True, False},{False, True}, {False, False}};
L2 = {{True, False, False}, {True, True, True},
{False, True, False}};
In[3]:=
Count[Equal@@@Transpose@{L1[[All, 2]], L2[[All, 3]]}, False]
Out[3]=
0
Checking we see
In[4]:=
L1[[All,2]]
Out[4]=
{False, True, False}
and
In[5]:=
L2[[All,3]]
Out[5]=
{False,True,False}
Clearly, both are the same verifying the count above is correct.
An alternative to In[3] using MapThread to do the same task would be:
In[6]:=
Count[MapThread[#1 == #2 &, {L1[[All, 2]], L2[[All, 3]]}], False]
Out[6]=
0
--
To reply via email subtract one hundred and four
Prev by Date:
**Re: DSolve and K$31, i am puzzled**
Next by Date:
**Re: InterpolatingFunctionAnatomy.m**
Previous by thread:
**Re: Count using pattern on two different matrices**
Next by thread:
**Re: Triangularize Matrix for Newmark method Keff=L^TDL**
| |