[R] Set a zero at minimum row by group

arun smartpink111 at yahoo.com
Tue Dec 18 18:02:38 CET 2012



Hi,
You could also use:
df$x_new<-unlist(lapply(split(df,df$ID),function(x) as.numeric(min(x[,2])!=x[,2])))
df
#  ID T x x_new
#1  1 1 1     0
#2  1 2 1     1
#3  1 3 1     1
#4  2 1 1     0
#5  2 4 1     1
#6  3 3 1     0
#7  3 5 1     1
#8  3 6 1     1
#9  3 8 1     1
A.K.

----- Original Message -----

From: Jose Iparraguirre <Jose.Iparraguirre at ageuk.org.uk>
To: Carlos Nasher <carlos.nasher at googlemail.com>; "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Tuesday, December 18, 2012 11:32 AM
Subject: Re: [R] Set a zero at minimum row by group

There may be more efficient ways, but here's one:

> x_new <- rep(0,nrow(df))
> x_new <- ifelse(df$T==min(T),0,1)

Regards,

José

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Carlos Nasher
Sent: 18 December 2012 14:10
To: r-help at r-project.org
Subject: [R] Set a zero at minimum row by group

Dear R Helpers,

I'm struggling with a data preparation problem. I feel that it is a quite
easy task but I don't get it done. I hope you can help me with that.

I have a data frame looking like this:

ID <- c(1,1,1,2,2,3,3,3,3)
T <- c(1,2,3,1,4,3,5,6,8)
x <- rep(1,9)
df <- data.frame(ID,T,x)

>df
ID T x
1 1 1
1 2 1
1 3 1
2 1 1
2 4 1
3 3 1
3 5 1
3 6 1
3 8 1

I want to manipulate the x column in a way that for each customer (ID) at
the minimum of T the x value is set to zero. The result should look like
this:

ID T x x_new
1 1 1     0
1 2 1     1
1 3 1     1
2 1 1     0
2 4 1     1
3 3 1     0
3 5 1     1
3 6 1     1
3 8 1     1

I already tried the aggregate() and apply() function, but I don't get the
result I'm looking for. I would glad if you could help me out.

Best regards,
Carlos

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