R help - Jun 2012 - conditional statement to replace values in dataframe with NA

Hello and thanks for helping.

#some data
L3 <- LETTERS[1:3]
dat1 <- data.frame(cbind(x=1, y=rep(1:3,2), fac=sample(L3, 6, replace=TRUE)))


#When x==1 and y==1 I want to replace the 1 values with NA

#I can select the rows I want:
dat2<-subset(dat1,x==1 & y==1)
#replace the 1 with NA
dat2$x<-rep(NA,nrow(dat2)
dat2$y<-rep(NA,nrow(dat2)

#select the other rows and rbind everything back together
#This is where I get stuck

#The end dataframe will look something like:

? x y ?fac
NA NA ? B
NA NA ? A
1 2 ? C
1 3 ? C
1 2 ? C
1 3 ? A

#Is there a better way to do this where I do not need to subset
perhaps using lapply?


Thanks,
Daisy

--
Daisy Englert Duursma
Department of Biological Sciences
Room E8C156
Macquarie University, North Ryde, NSW 2109
Australia

Tel +61 2 9850 9256

Hi,

Try this,> dat1 <- data.frame(x=rep(1,6),y=rep(1:3,2), fac=sample(L3, 6,
replace=TRUE))
> dat1
? x y fac
1 1 1?? C
2 1 2?? B
3 1 3?? B
4 1 1?? A
5 1 2?? B
6 1 3?? B
> dat1[dat1$x==1&dat1$y==1,1:2]<-NA
> dat1
?? x? y fac
1 NA NA?? C
2? 1? 2?? B
3? 1? 3?? B
4 NA NA?? A
5? 1? 2?? B
6? 1? 3?? B


A.K.



----- Original Message -----
From: Daisy Englert Duursma <daisy.duursma at gmail.com>
To: "r-help at R-project.org" <r-help at r-project.org>
Cc: 
Sent: Wednesday, June 6, 2012 11:58 PM
Subject: [R] conditional statement to replace values in dataframe with NA

Hello and thanks for helping.

#some data
L3 <- LETTERS[1:3]
dat1 <- data.frame(cbind(x=1, y=rep(1:3,2), fac=sample(L3, 6, replace=TRUE)))


#When x==1 and y==1 I want to replace the 1 values with NA

#I can select the rows I want:
dat2<-subset(dat1,x==1 & y==1)
#replace the 1 with NA
dat2$x<-rep(NA,nrow(dat2)
dat2$y<-rep(NA,nrow(dat2)

#select the other rows and rbind everything back together
#This is where I get stuck

#The end dataframe will look something like:

? x y ?fac
NA NA ? B
NA NA ? A
1 2 ? C
1 3 ? C
1 2 ? C
1 3 ? A

#Is there a better way to do this where I do not need to subset
perhaps using lapply?


Thanks,
Daisy

--
Daisy Englert Duursma
Department of Biological Sciences
Room E8C156
Macquarie University, North Ryde, NSW 2109
Australia

Tel +61 2 9850 9256

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Have you read "An Intro to R?" If not,please do so before posting
further. The way you are going about things makes me think you
haven't, but ...

This **is** a slightly tricky application of indexing, if I understand
you correctly. Here are two essentially identical ways to do it, but
the second is a little trickier

## First
> dat1[dat1$x==1 & dat1$y==1,1:2] <- rep(NA,2)
> dat1
     x    y fac
1 <NA> <NA>   A
2    1    2   B
3    1    3   A
4 <NA> <NA>   C
5    1    2   A
6    1    3   C

##Slightly trickier version using with() to avoid explicit extraction
from data frame
## Reconstitute dat1
> dat1
  x y fac
1 1 1   C
2 1 2   C
3 1 3   B
4 1 1   B
5 1 2   C
6 1 3   B

dat1 <- with(dat1,{dat1[x==1 & y==1,1:2] <- rep(NA,2);
dat1})
> dat1
     x    y fac
1 <NA> <NA>   B
2    1    2   A
3    1    3   A
4 <NA> <NA>   C
5    1    2   A
6    1    3   B

## ?with for explanation

-- Bert

On Wed, Jun 6, 2012 at 8:58 PM, Daisy Englert Duursma
<daisy.duursma at gmail.com> wrote:
> Hello and thanks for helping.
>
> #some data
> L3 <- LETTERS[1:3]
> dat1 <- data.frame(cbind(x=1, y=rep(1:3,2), fac=sample(L3, 6,
replace=TRUE)))
>
>
> #When x==1 and y==1 I want to replace the 1 values with NA
>
> #I can select the rows I want:
> dat2<-subset(dat1,x==1 & y==1)
> #replace the 1 with NA
> dat2$x<-rep(NA,nrow(dat2)
> dat2$y<-rep(NA,nrow(dat2)
>
> #select the other rows and rbind everything back together
> #This is where I get stuck
>
> #The end dataframe will look something like:
>
> ? x y ?fac
> NA NA ? B
> NA NA ? A
> 1 2 ? C
> 1 3 ? C
> 1 2 ? C
> 1 3 ? A
>
> #Is there a better way to do this where I do not need to subset
> perhaps using lapply?
>
>
> Thanks,
> Daisy
>
> --
> Daisy Englert Duursma
> Department of Biological Sciences
> Room E8C156
> Macquarie University, North Ryde, NSW 2109
> Australia
>
> Tel +61 2 9850 9256
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

Thanks, problem solved.

On Thu, Jun 7, 2012 at 1:58 PM, Daisy Englert Duursma
<daisy.duursma at gmail.com> wrote:
> Hello and thanks for helping.
>
> #some data
> L3 <- LETTERS[1:3]
> dat1 <- data.frame(cbind(x=1, y=rep(1:3,2), fac=sample(L3, 6,
replace=TRUE)))
>
>
> #When x==1 and y==1 I want to replace the 1 values with NA
>
> #I can select the rows I want:
> dat2<-subset(dat1,x==1 & y==1)
> #replace the 1 with NA
> dat2$x<-rep(NA,nrow(dat2)
> dat2$y<-rep(NA,nrow(dat2)
>
> #select the other rows and rbind everything back together
> #This is where I get stuck
>
> #The end dataframe will look something like:
>
> ? x y ?fac
> NA NA ? B
> NA NA ? A
> 1 2 ? C
> 1 3 ? C
> 1 2 ? C
> 1 3 ? A
>
> #Is there a better way to do this where I do not need to subset
> perhaps using lapply?
>
>
> Thanks,
> Daisy
>
> --
> Daisy Englert Duursma
> Department of Biological Sciences
> Room E8C156
> Macquarie University, North Ryde, NSW 2109
> Australia
>
> Tel +61 2 9850 9256


-- 
Daisy Englert Duursma
Department of Biological Sciences
Room E8C156
Macquarie University, North Ryde, NSW 2109
Australia

Tel +61 2 9850 9256