R help - May 2005 - how to get such a subset of a matrix?

Hi everybody,
Maybe this question is quite simple but i just don't know how to make it.
I have a matrix a somewhat like this one but bigger:
> a
f g h i j k
a NA NA 11 16 21 26
b NA NA 12 17 22 27
c NA 8 13 18 23 28
d NA 9 14 19 24 29
e NA 10 15 20 25 30
And i want to get the rows which at most have 2 Na.
Thanks in advance.
Shi Jiantao

	[[alternative HTML version deleted]]

R> a <- matrix(1:36,6,6)
R> is.na(a[row(a)<col(a)]) <- TRUE
R> a
      [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    1   NA   NA   NA   NA   NA
[2,]    2    8   NA   NA   NA   NA
[3,]    3    9   15   NA   NA   NA
[4,]    4   10   16   22   NA   NA
[5,]    5   11   17   23   29   NA
[6,]    6   12   18   24   30   36

 > a[apply(a,1,function(x){sum(is.na(x))<=2}),]
      [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    4   10   16   22   NA   NA
[2,]    5   11   17   23   29   NA
[3,]    6   12   18   24   30   36
 >

Hope this helps

rksh

On May 6, 2005, at 02:21 pm, Xiao Shi wrote:
> Hi everybody,
> Maybe this question is quite simple but i just don't know how to make 
> it.
> I have a matrix a somewhat like this one but bigger:
>> a
> f g h i j k
> a NA NA 11 16 21 26
> b NA NA 12 17 22 27
> c NA 8 13 18 23 28
> d NA 9 14 19 24 29
> e NA 10 15 20 25 30
> And i want to get the rows which at most have 2 Na.
> Thanks in advance.
> Shi Jiantao
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> 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
>
>
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743

Xiao Shi wrote on 5/6/2005 6:21 AM:
> Hi everybody,
> Maybe this question is quite simple but i just don't know how to make
it.
> I have a matrix a somewhat like this one but bigger:
> 
>>a
> 
> f g h i j k
> a NA NA 11 16 21 26
> b NA NA 12 17 22 27
> c NA 8 13 18 23 28
> d NA 9 14 19 24 29
> e NA 10 15 20 25 30
> And i want to get the rows which at most have 2 Na.
> Thanks in advance.
> Shi Jiantao
> 

How about:

a[rowSums(is.na(a)) < 2, ]

HTH,

--sundar

one way to do it is:

mat <- matrix(rnorm(20*20), 20, 20)
mat[sample(400, 40)] <- NA
#####
mat
mat[rowSums(is.na(mat)) <= 2, ]


I hope it helps.

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: "Xiao Shi" <bioconductor.cn at gmail.com>
To: <r-help at stat.math.ethz.ch>
Sent: Friday, May 06, 2005 3:21 PM
Subject: [R] how to get such a subset of a matrix?

> Hi everybody,
> Maybe this question is quite simple but i just don't know how to 
> make it.
> I have a matrix a somewhat like this one but bigger:
>> a
> f g h i j k
> a NA NA 11 16 21 26
> b NA NA 12 17 22 27
> c NA 8 13 18 23 28
> d NA 9 14 19 24 29
> e NA 10 15 20 25 30
> And i want to get the rows which at most have 2 Na.
> Thanks in advance.
> Shi Jiantao
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> 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
>

Try:

  a[rowSums(is.na(a)) <= 2, ]

Andy
> From: Xiao Shi
> 
> Hi everybody,
> Maybe this question is quite simple but i just don't know how 
> to make it.
> I have a matrix a somewhat like this one but bigger:
> > a
> f g h i j k
> a NA NA 11 16 21 26
> b NA NA 12 17 22 27
> c NA 8 13 18 23 28
> d NA 9 14 19 24 29
> e NA 10 15 20 25 30
> And i want to get the rows which at most have 2 Na.
> Thanks in advance.
> Shi Jiantao
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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
> 
> 
>