R help - Jul 2006 - replace values?

Dear friends,
  i have a dataset like this:
x y z
1 2 3
2 3 1
3 2 1
1 1 3
2 1 2
3 2 3
2 1 1
I want to replace x with the following values:1<-a,2<-b,3<-c,4<-d;
             replace y with the following
values:1<-b,2<-a,3<-c,4<-d;
             replace z with the following
values:1<-d,2<-c,3<-b,4<-a;
Finally,select two subsets:
1. if x='a';
2.x='a' and y='a';
 thanks very much!



-- 
Kind Regards,
Zhi Jie,Zhang ,PHD
Department of Epidemiology
School of Public Health
Fudan University
Tel:86-21-54237149

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On 07/02/06 12:39, zhijie zhang wrote:
> Dear friends,
>   i have a dataset like this:
> x y z
> 1 2 3
> 2 3 1
> 3 2 1
> 1 1 3
> 2 1 2
> 3 2 3
> 2 1 1
> I want to replace x with the following
values:1<-a,2<-b,3<-c,4<-d;
>              replace y with the following
values:1<-b,2<-a,3<-c,4<-d;
>              replace z with the following
values:1<-d,2<-c,3<-b,4<-a;
Here's one way.  Call your dataset M, and assume it is a
data.frame.  This method of replacement works best when you are
replacing consecutive integers, as you are.  Note that X[1] is
"a", X[2] is "b" and so on.

X <- c("a","b","c","d")
Y <- c("b","a","c","d")
Z <- c("d","c","b","a")
M$x <- X[M$x]
M$y <- Y[M$y]
M$z <- Z[M$z]
> Finally,select two subsets:
> 1. if x='a';
> 2.x='a' and y='a';
M[M$x=="a",]
M[M$x=="a" & M$y=="a",]

The subsets will be rows.  I'm not sure that's what you mean.

Jon
-- 
Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page: http://www.sas.upenn.edu/~baron

# reproducing your example
xx<-"x y z
+ 1 2 3
+ 2 3 1
+ 3 2 1
+ 1 1 3
+ 2 1 2
+ 3 2 3
+ 2 1 1"

# you did not tell us the class of your data, assuming data.frame
df<-read.table(textConnection(xx),header=T,colClasses="factor")

# a clean way to do what you want is using factors with ?levels
# (note that data has already been read as factor)
levels(df$x)<-c("a","b","c","d")
levels(df$y)<-c("b","a","c","d")
levels(df$z)<-c("d","c","b","a")

subset(df,x=="a")
  x y z
1 a a b
4 a b b
subset(df,x=="a"&y=="a")
  x y z
1 a a b


HTH, m


zhijie zhang wrote:
> Dear friends,
>   i have a dataset like this:
> x y z
> 1 2 3
> 2 3 1
> 3 2 1
> 1 1 3
> 2 1 2
> 3 2 3
> 2 1 1
> I want to replace x with the following
values:1<-a,2<-b,3<-c,4<-d;
>              replace y with the following
values:1<-b,2<-a,3<-c,4<-d;
>              replace z with the following
values:1<-d,2<-c,3<-b,4<-a;
> Finally,select two subsets:
> 1. if x='a';
> 2.x='a' and y='a';
>  thanks very much!