R help - Feb 2005 - Converting a list to a matrix - I still don't think I have it right

Hi

We have touched on this before, but I don't think I quite got it right.

So I have a list, each element of which is a a vector of 2 numbers:
> l2
$cat000_a01
[1] 0.3429944 4.5138244

$cat000_a02
[1] 0.1929336 4.3064944

$cat000_a03
[1] -0.2607796  4.1551591

What I actually want to convert this into is a matrix with the names
(cat000_a01 etc) as row names, the first element of each of the vectors
forming the first column of the new matrix, and the second element of
each of the vectors forming the second column:

cat000_a01	0.3429944	4.5138244
cat000_a02	0.1929336	4.3064944
cat000_a03	-0.2607796  4.1551591

What was suggested on the list last time was
matrix(unlist(mylist),nrow=length(mylist)).  But if I do this I get:
> matrix(unlist(l2),nrow=length(l2))
          [,1]       [,2]
[1,] 0.3429944  4.3064944
[2,] 4.5138244 -0.2607796
[3,] 0.1929336  4.1551591

Which is not what I want.  Here, the second element of the first vector
in my list has gone into the first column of the new matrix, and that's
not what I want at all.

Any more help would be appreciated.

Thanks
Mick

Mick,

Does this do it?

mymat <- do.call('rbind',l2)
rownames(mymat) <- names(l2)

Sean

On Feb 17, 2005, at 9:36 AM, michael watson ((IAH-C)) wrote:
> Hi
>
> We have touched on this before, but I don't think I quite got it right.
>
> So I have a list, each element of which is a a vector of 2 numbers:
>
>> l2
> $cat000_a01
> [1] 0.3429944 4.5138244
>
> $cat000_a02
> [1] 0.1929336 4.3064944
>
> $cat000_a03
> [1] -0.2607796  4.1551591
>
> What I actually want to convert this into is a matrix with the names
> (cat000_a01 etc) as row names, the first element of each of the vectors
> forming the first column of the new matrix, and the second element of
> each of the vectors forming the second column:
>
> cat000_a01	0.3429944	4.5138244
> cat000_a02	0.1929336	4.3064944
> cat000_a03	-0.2607796  4.1551591
>
> What was suggested on the list last time was
> matrix(unlist(mylist),nrow=length(mylist)).  But if I do this I get:
>
>> matrix(unlist(l2),nrow=length(l2))
>           [,1]       [,2]
> [1,] 0.3429944  4.3064944
> [2,] 4.5138244 -0.2607796
> [3,] 0.1929336  4.1551591
>
> Which is not what I want.  Here, the second element of the first vector
> in my list has gone into the first column of the new matrix, and that's
> not what I want at all.
>
> Any more help would be appreciated.
>
> Thanks
> Mick
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html

This should do it:

matrix(unlist(mylist),nrow=length(mylist), by=T)


--------------------------------------------------------------------------
Ravi Varadhan, Ph.D.
Assistant Professor,  The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email:  rvaradhan at jhmi.edu
--------------------------------------------------------------------------
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch [mailto:r-help-
> bounces at stat.math.ethz.ch] On Behalf Of michael watson (IAH-C)
> Sent: Thursday, February 17, 2005 9:37 AM
> To: r-help at r-project.org
> Subject: [R] Converting a list to a matrix - I still don't think I have
> itright
> 
> Hi
> 
> We have touched on this before, but I don't think I quite got it right.
> 
> So I have a list, each element of which is a a vector of 2 numbers:
> 
> > l2
> $cat000_a01
> [1] 0.3429944 4.5138244
> 
> $cat000_a02
> [1] 0.1929336 4.3064944
> 
> $cat000_a03
> [1] -0.2607796  4.1551591
> 
> What I actually want to convert this into is a matrix with the names
> (cat000_a01 etc) as row names, the first element of each of the vectors
> forming the first column of the new matrix, and the second element of
> each of the vectors forming the second column:
> 
> cat000_a01	0.3429944	4.5138244
> cat000_a02	0.1929336	4.3064944
> cat000_a03	-0.2607796  4.1551591
> 
> What was suggested on the list last time was
> matrix(unlist(mylist),nrow=length(mylist)).  But if I do this I get:
> 
> > matrix(unlist(l2),nrow=length(l2))
>           [,1]       [,2]
> [1,] 0.3429944  4.3064944
> [2,] 4.5138244 -0.2607796
> [3,] 0.1929336  4.1551591
> 
> Which is not what I want.  Here, the second element of the first vector
> in my list has gone into the first column of the new matrix, and that's
> not what I want at all.
> 
> Any more help would be appreciated.
> 
> Thanks
> Mick
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-
> guide.html

mat <- matrix(unlist(l2), nrow=length(l2), byrow=TRUE)
rownames(mat) <- names(l2)
mat

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "michael watson (IAH-C)" <michael.watson at bbsrc.ac.uk>
To: <r-help at r-project.org>
Sent: Thursday, February 17, 2005 3:36 PM
Subject: [R] Converting a list to a matrix - I still don't think I 
have itright

> Hi
>
> We have touched on this before, but I don't think I quite got it 
> right.
>
> So I have a list, each element of which is a a vector of 2 numbers:
>
>> l2
> $cat000_a01
> [1] 0.3429944 4.5138244
>
> $cat000_a02
> [1] 0.1929336 4.3064944
>
> $cat000_a03
> [1] -0.2607796  4.1551591
>
> What I actually want to convert this into is a matrix with the names
> (cat000_a01 etc) as row names, the first element of each of the 
> vectors
> forming the first column of the new matrix, and the second element 
> of
> each of the vectors forming the second column:
>
> cat000_a01 0.3429944 4.5138244
> cat000_a02 0.1929336 4.3064944
> cat000_a03 -0.2607796  4.1551591
>
> What was suggested on the list last time was
> matrix(unlist(mylist),nrow=length(mylist)).  But if I do this I get:
>
>> matrix(unlist(l2),nrow=length(l2))
>          [,1]       [,2]
> [1,] 0.3429944  4.3064944
> [2,] 4.5138244 -0.2607796
> [3,] 0.1929336  4.1551591
>
> Which is not what I want.  Here, the second element of the first 
> vector
> in my list has gone into the first column of the new matrix, and 
> that's
> not what I want at all.
>
> Any more help would be appreciated.
>
> Thanks
> Mick
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
>

Does

do.call("rbind", l2)

do what you want?

-roger

michael watson (IAH-C) wrote:
> Hi
> 
> We have touched on this before, but I don't think I quite got it right.
> 
> So I have a list, each element of which is a a vector of 2 numbers:
> 
> 
>>l2
> 
> $cat000_a01
> [1] 0.3429944 4.5138244
> 
> $cat000_a02
> [1] 0.1929336 4.3064944
> 
> $cat000_a03
> [1] -0.2607796  4.1551591
> 
> What I actually want to convert this into is a matrix with the names
> (cat000_a01 etc) as row names, the first element of each of the vectors
> forming the first column of the new matrix, and the second element of
> each of the vectors forming the second column:
> 
> cat000_a01	0.3429944	4.5138244
> cat000_a02	0.1929336	4.3064944
> cat000_a03	-0.2607796  4.1551591
> 
> What was suggested on the list last time was
> matrix(unlist(mylist),nrow=length(mylist)).  But if I do this I get:
> 
> 
>>matrix(unlist(l2),nrow=length(l2))
> 
>           [,1]       [,2]
> [1,] 0.3429944  4.3064944
> [2,] 4.5138244 -0.2607796
> [3,] 0.1929336  4.1551591
> 
> Which is not what I want.  Here, the second element of the first vector
> in my list has gone into the first column of the new matrix, and that's
> not what I want at all.
> 
> Any more help would be appreciated.
> 
> Thanks
> Mick
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 
-- 
Roger D. Peng
http://www.biostat.jhsph.edu/~rpeng/

Hi Michael

On 17 Feb 2005 at 14:36, michael watson (IAH-C) wrote:
> Hi
> 
> We have touched on this before, but I don't think I quite got it
> right.
> 
> So I have a list, each element of which is a a vector of 2 numbers:
> 
> > l2
> $cat000_a01
> [1] 0.3429944 4.5138244
> 
> $cat000_a02
> [1] 0.1929336 4.3064944
> 
> $cat000_a03
> [1] -0.2607796  4.1551591
> 
> What I actually want to convert this into is a matrix with the names
> (cat000_a01 etc) as row names, the first element of each of the
> vectors forming the first column of the new matrix, and the second
> element of each of the vectors forming the second column:
> 
> cat000_a01	0.3429944	4.5138244
> cat000_a02	0.1929336	4.3064944
> cat000_a03	-0.2607796  4.1551591
> 
> What was suggested on the list last time was
> matrix(unlist(mylist),nrow=length(mylist)).  But if I do this I get:
> 
> > matrix(unlist(l2),nrow=length(l2))
>           [,1]       [,2]
> [1,] 0.3429944  4.3064944
> [2,] 4.5138244 -0.2607796
> [3,] 0.1929336  4.1551591
Try byrow =TRUE argument
> x<-list(a=c(1,2), b=c(4,5), d= c(10,12))
> matrix(unlist(x),nrow=length(x), byrow=T)
     [,1] [,2]
[1,]    1    2
[2,]    4    5
[3,]   10   12


Cheers 
Petr



> Which is not what I want.  Here, the second element of the first
> vector in my list has gone into the first column of the new matrix,
> and that's not what I want at all.
> 
> Any more help would be appreciated.
> 
> Thanks
> Mick
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
Petr Pikal
petr.pikal at precheza.cz

"michael watson (IAH-C)" <michael.watson at bbsrc.ac.uk> writes:
> Hi
> 
> We have touched on this before, but I don't think I quite got it right.
> 
> So I have a list, each element of which is a a vector of 2 numbers:
> 
> > l2
> $cat000_a01
> [1] 0.3429944 4.5138244
> 
> $cat000_a02
> [1] 0.1929336 4.3064944
> 
> $cat000_a03
> [1] -0.2607796  4.1551591
> 
> What I actually want to convert this into is a matrix with the names
> (cat000_a01 etc) as row names, the first element of each of the vectors
> forming the first column of the new matrix, and the second element of
> each of the vectors forming the second column:
> 
> cat000_a01	0.3429944	4.5138244
> cat000_a02	0.1929336	4.3064944
> cat000_a03	-0.2607796  4.1551591
do.call("rbind", list)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907