[R] Set a zero at minimum row by group

[David L Carlson]

This is a bit simpler:

> df$x_new <- ave(df$T, df$ID, FUN=function(x)x!=min(x))
> df
  ID T x x_new
1  1 1 0     0
2  1 2 1     1
3  1 3 1     1
4  2 1 0     0
5  2 4 1     1
6  3 3 0     0
7  3 5 1     1
8  3 6 1     1
9  3 8 1     1

Are you sure there are no ties for the minimum value? 

----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of William Dunlap
> Sent: Tuesday, December 18, 2012 10:45 AM
> To: Carlos Nasher; r-help at r-project.org
> Subject: Re: [R] Set a zero at minimum row by group
> 
> You should show what you tried with aggregate and tapply.
> 
> You could use ave():
>   > wm <- as.logical(ave(df$T, df$ID, FUN=function(x)x==min(x)))
>   > df$x_new <- df$x
>   > df$x_new[wm] <- 0
>   > df
>     ID T x x_new
>   1  1 1 1     0
>   2  1 2 1     1
>   3  1 3 1     1
>   4  2 1 1     0
>   5  2 4 1     1
>   6  3 3 1     0
>   7  3 5 1     1
>   8  3 6 1     1
>   9  3 8 1     1
> 
> (The as.logical is there because ave() coerces the logical output of
> FUN to the type of df$T, numeric, and we need to convert it back to
> logical.)
> 
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
> 
> 
> > -----Original Message-----
> > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf
> > Of Carlos Nasher
> > Sent: Tuesday, December 18, 2012 6:10 AM
> > 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
> >
> > 	[[alternative HTML version deleted]]
> >
> > ______________________________________________
> > 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.
> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.