Subsetting with missing data

HI,

Try this:
subset(a,y==0)
#??? x y
#2?? 2 0
#5?? 5 0
#10 10 0

#or
subset(a,y%in%0)
#??? x y
#2?? 2 0
#5?? 5 0
#10 10 0


A.K.



----- Original Message -----
From: Robin Jeffries <rjeffries at ucla.edu>
To: r-help at r-project.org
Cc: 
Sent: Wednesday, August 15, 2012 4:06 PM
Subject: [R] Subsetting with missing data

Simply put, I want to subset the data frame 'a' where 'y=0'.

a <- as.data.frame(cbind(x=1:10, y=c(1,0,NA,1,0,NA,NA,1,1,0)))
a

? ? x? y
1?  1? 1
2?  2? 0
3?  3 NA
4?  4? 1
5?  5? 0
6?  6 NA
7?  7 NA
8?  8? 1
9?  9? 1
10 10? 0

names(a)

[1] "x" "y"

table(a$y)

0 1
3 4

table(a$y, useNA="always")

?  0? ? 1 <NA>
?  3? ? 4? ? 3

b <- a[a$y==0,]
b

? ? ? x? y
2? ?  2? 0
NA?  NA NA
5? ?  5? 0
NA.1 NA NA
NA.2 NA NA
10?  10? 0

is(a$y)

[1] "numeric" "vector"


Instead of only pulling the rows where a$y==0, i'm getting where they're 0,
OR NA. ? Again I feel like either something was changed when I wasn't
looking.. or I'm reaaaaaaly forgetting something important.

Thanks,

Robin Jeffries
MS, DrPH Candidate
Department of Biostatistics,
UCLA
530-633-STAT(7828)
rjeffries at ucla.edu

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