[R] How to do it through 1 step?

[arun]

Hi,
How about this?

set.seed(5)
dat<-data.frame(x=sample(1:20,6,replace=TRUE),a=sample(20:40,6,replace=TRUE))
 dat1<-within(dat,{f=a/median(a);x_new=x*f})
 dat1
#   x  a     x_new         f
#1  5 31  5.081967 1.0163934
#2 14 36 16.524590 1.1803279
#3 19 40 24.918033 1.3114754
#4  6 22  4.327869 0.7213115
#5  3 25  2.459016 0.8196721
#6 15 30 14.754098 0.9836066

#or
 res<-do.call(data.frame,lapply(lapply(1,function(y) dat),function(y) {y$f<-y$a/median(y$a);y$x_new<-y$f*y$x;y}))
A.K.






________________________________
From: meng <laomeng_3 at 163.com>
To: arun <smartpink111 at yahoo.com> 
Cc: R help <r-help at r-project.org> 
Sent: Monday, December 24, 2012 5:29 AM
Subject: Re:Re: [R] How to do it through 1 step?


Yes,this is my final solution,but if I wanna add many new variables,and maybe the following "new variables" are computed based on the previous " new variables", this solution maybe difficult.








At 2012-12-24 17:01:03,arun <smartpink111 at yahoo.com> wrote:
>HI,
>
>Not sure if this works for you.
>set.seed(5)
>dat<-data.frame(x=sample(1:20,6,replace=TRUE),a=sample(20:40,6,replace=TRUE))
> dat1<-transform(dat,f=a/median(a),x_new=x*(a/median(a)))
> head(dat1,2)
>#   x  a        f     x_new
>#1  5 31 1.016393  5.081967
>#2 14 36 1.180328 16.524590
>A.K.
>
>
>
>
>----- Original Message -----
>From: meng <laomeng_3 at 163.com>
>To: r-help at r-project.org
>Cc: 
>Sent: Monday, December 24, 2012 12:55 AM
>Subject: [R] How to do it through 1 step?
>
>A data set(dat),has 2 variables: x and a, and 100 rows.
>
>I wanna add 2 variables,and call the new data set dat1:
>var1:f = a/median(a)
>var2:x_new = x*f
>
>My solution:
>dat1<-transform(dat,f = a/median(a),x_new = x*f)
>But gets error reply which says that "f" is not exits since dat has no variables called "f".
>
>So I have to do through 2 steps:
>dat0<-transform(dat,f=a/median(a))
>dat1<-transform(dat0,x_new=x*f)
>
>How to do it through 1 step?
>
>Many thanks!
>
>
>    [[alternative HTML version deleted]]
>
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