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From: forkandwait w on 5 May 2010 16:03
Is there a *general* or standard way to extract a two dim matrix in which data is nested hierarchically along the rows into an N dim matrix? I am looking for a general solution, since I can do it ad hoc just fine.

I have the following (best viewed in fixed width):

x =
yr1 yr2 yr3 yr4 yr5
county1/male 1 2 3 4 5
county1/fem 10 20 30 40 50
county2/male 6 7 8 9 10
county2/female 60 70 80 90 100
county3/male 11 12 13 14 15
county3/female 110 120 130 140 150

I would like to transform it into a 3 by 2 by 5 matrix:

ans(:,:,1) =

1 2 3 4 5
6 7 8 9 10
11 12 13 14 15

ans(:,:,2) =

10 20 30 40 50
60 70 80 90 100
110 120 130 140 150
From: Walter Roberson on 5 May 2010 16:14
forkandwait w wrote:
> Is there a *general* or standard way to extract a two dim matrix in
> which data is nested hierarchically along the rows into an N dim
> matrix? I am looking for a general solution, since I can do it ad hoc
> just fine.
>
> I have the following (best viewed in fixed width):
>
> x =
> yr1 yr2 yr3 yr4 yr5 county1/male 1
> 2 3 4 5
> county1/fem 10 20 30 40 50
> county2/male 6 7 8 9 10
> county2/female 60 70 80 90 100
> county3/male 11 12 13 14 15
> county3/female 110 120 130 140 150
>
> I would like to transform it into a 3 by 2 by 5 matrix:

In your example, male and female strictly alternate. Is that a
certainty? If so, then once you have removed the leading header column
(not sure the 'county1/male' part is real or just explanitory):

cat(3,x(1:2:end,:),x(2:2:end))


If the 'county1/male' part is a real field and the data is not certain
to already be interweaved in the order you want to extract it, then the
matter becomes more complicated.
From: Doug Schwarz on 5 May 2010 16:17
forkandwait w wrote:
> Is there a *general* or standard way to extract a two dim matrix in
> which data is nested hierarchically along the rows into an N dim
> matrix? I am looking for a general solution, since I can do it ad hoc
> just fine.
>
> I have the following (best viewed in fixed width):
>
> x =
> yr1 yr2 yr3 yr4 yr5 county1/male 1
> 2 3 4 5
> county1/fem 10 20 30 40 50
> county2/male 6 7 8 9 10
> county2/female 60 70 80 90 100
> county3/male 11 12 13 14 15
> county3/female 110 120 130 140 150
>
> I would like to transform it into a 3 by 2 by 5 matrix:
> ans(:,:,1) =
>
> 1 2 3 4 5
> 6 7 8 9 10
> 11 12 13 14 15
>
> ans(:,:,2) =
>
> 10 20 30 40 50
> 60 70 80 90 100
> 110 120 130 140 150

cols = 5;
rows = 3;
planes = 2;
permute(reshape(x.',cols,planes,rows),[3 1 2])

where cols, rows and planes are what you desire in the final result.

--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.
From: forkandwait w on 5 May 2010 19:18
> cols = 5;
> rows = 3;
> planes = 2;
> permute(reshape(x.',cols,planes,rows),[3 1 2])
>
> where cols, rows and planes are what you desire in the final result.

Has any kind soul written a tutorial to explain this kind of matrix manipulation?
From: Doug Schwarz on 5 May 2010 21:56
In article <hrsubf$stl$1(a)fred.mathworks.com>,
"forkandwait w" <forkandwait(a)gmail.com> wrote:

> > cols = 5;
> > rows = 3;
> > planes = 2;
> > permute(reshape(x.',cols,planes,rows),[3 1 2])
> >
> > where cols, rows and planes are what you desire in the final result.
>
> Has any kind soul written a tutorial to explain this kind of matrix
> manipulation?

I'm not sure if I know how to teach it.

To solve such problems it's important that you know how MATLAB stores
the numbers in an array. The operation X(:) will turn any array X into
a column vector without moving any numbers so that's a good way to
explore and try things. Also, reshape will change the size of an array
without moving anything. The operators .' (transpose) and permute
(transpose is really just permute(X,[2 1]) ) will move numbers around so
play with them and see what happens.

Maybe it's possible to formalize what I did, but I just did it
intuitively. It helps that I've been using MATLAB for more than 20
years.

--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.
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