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Topic: data extraction from matrix to use in another matrix
Replies: 26   Last Post: Oct 22, 2013 4:57 PM

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 dpb Posts: 9,850 Registered: 6/7/07
Re: data extraction from matrix to use in another matrix
Posted: Oct 19, 2013 1:22 PM

On 10/19/2013 11:03 AM, walter Mulvany wrote:
> I'm writing a code for finite element analysis and I don't know how to
> read a value from a matrix (A) and use it as a pointer to direct me to
> values in another matrix.
> Here is a sample of the problem.

...

> connectivity=[1,1,2;2,1,3;3,2,3]
...
> coordinates=[1,0,0;2,2,0;3,1,2]
...
> I need to read element's 1 node(a) which in this case is 1, and use that
> 1 to direct me to the node 1, extract the x and y coordinate from node
> 1, and create a matrix.

...

Well, it's not clear which you're after, but it's simple enough to find
a location in an array by value and get the associated information from
some other for that.

If ask for points in connectivity array that include node 1, that's given by

>> conn=[1,1,2;2,1,3;3,2,3];
>> coord=[1,0,0;2,2,0;3,1,2];
>> idx=any(conn==1,2) % row indices of any connections w/ a '1'

idx =
1
1
0
>> coord(idx,:) % get those rows' coordinates...
ans =
1 0 0
2 2 0
>> coord(any(conn==1,2),:) % do it w/o the intermediate variable
ans =
1 0 0
2 2 0
>>

Look in subject index for "logical addressing" ...

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Date Subject Author
10/19/13 walter Mulvany
10/19/13 dpb
10/19/13 walter Mulvany
10/19/13 dpb
10/19/13 walter Mulvany
10/20/13 dpb
10/20/13 walter Mulvany
10/20/13 dpb
10/20/13 walter Mulvany
10/21/13 walter Mulvany
10/21/13 dpb
10/21/13 dpb
10/21/13 walter Mulvany
10/21/13 dpb
10/21/13 walter Mulvany
10/22/13 walter Mulvany
10/22/13 dpb
10/22/13 walter Mulvany
10/22/13 walter Mulvany
10/22/13 dpb
10/22/13 walter Mulvany
10/22/13 dpb
10/22/13 dpb
10/22/13 walter Mulvany
10/22/13 dpb
10/22/13 dpb
10/20/13 dpb