[R] A query about na.omit

[(Ted Harding)]

On 01-Apr-09 15:49:40, Jose Iparraguirre D'Elia wrote:
> Dear all,
> Say I have the following dataset:
>  
>> DF
>         x     y     z
> [1]   1     1     1
> [2]   2     2     2
> [3]   3     3    NA
> [4]   4   NA   4
> [5]  NA  5     5
>  
> And I want to omit all the rows which have NA, but only in columns X
> and Y, so that I get:
>  
>  x  y  z
> 1  1  1
> 2  2  2
> 3  3  NA

Roll up your sleeves, and spell out in detail the condition you need:

  DF<-data.frame(x=c(1,2,3,4,NA),y=c(1,2,3,NA,5),z=c(1,2,NA,4,5))
  DF
#    x  y  z
# 1  1  1  1
# 2  2  2  2
# 3  3  3 NA
# 4  4 NA  4
# 5 NA  5  5

  DF[!(is.na(rowSums(DF[,(1:2)]))),]
#   x y  z
# 1 1 1  1
# 2 2 2  2
# 3 3 3 NA

Hoping this helps,
Ted.

> If I use na.omit(DF), I would delete the row for which z=NA, obtaining
> thus
>  
> x y z
> 1 1 1
> 2 2 2
>  
> But this is not what I want, of course. 
> If I use na.omit(DF[,1:2]), then I obtain
>  
> x y 
> 1 1
> 2 2
> 3 3
>  
> which is OK for x and y columns, but I wouldn't get the corresponding
> values for z (ie 1 2 NA)
>  
> Any suggestions about how to obtain the desired results efficiently
> (the actual dataset has millions of records and almost 50 columns, and
> I would apply the procedure on 12 of these columns)?
>  
> Sincerely,
>  
> Jose Luis 
>  
> Jose Luis Iparraguirre
> Senior Research Economist 
> Economic Research Institute of Northern Ireland
>  
>  
> 
>       [[alternative HTML version deleted]]
> 
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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
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Date: 01-Apr-09                                       Time: 18:00:53
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