[R] Set a zero at minimum row by group

[David L Carlson]

Just noticed that I used a modified copy of df. It should be

> 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
-------
David

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of David L Carlson
> Sent: Tuesday, December 18, 2012 4:30 PM
> To: 'William Dunlap'; 'Carlos Nasher'; r-help at r-project.org
> Subject: Re: [R] Set a zero at minimum row by group
> 
> 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
> > 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
> 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.