R help - Jan 2003 - (no subject)

Dear Mailing List,

If I wanted a data set of twenty standard normal results, I would type:

x<-rnorm(20)

If I then wanted to make all the negative results in that data set to be 
listed as zero I would then type in:

x[x<0]<-0

However, I now want to discard the values that are zero, but I want to know 
which values out of the original data set which I truncated to zeros I 
discarded. How is the best way of doing this? Do I use match(x,0) / 
(1:length(x))[x==0] ? How do I discard the values as well as wanting the 
original data set values. All suggestions would be greatly appreciated.

Thank you,

James Hutton

	[[alternate HTML version deleted]]

James,

I think you want to try using index vectors.
index <- c(1:length(x))
negs <- index[x<0]
nonnegs <- index[x>=0]

Then, if you want the negative values, just use
negativevalues <- x[negs]

HTH
steve

Jmshttn at aol.com wrote:
> Dear Mailing List,
>
> If I wanted a data set of twenty standard normal results, I would type:
>
> x<-rnorm(20)
>
> If I then wanted to make all the negative results in that data set to be
> listed as zero I would then type in:
>
> x[x<0]<-0
>
> However, I now want to discard the values that are zero, but I want to know
> which values out of the original data set which I truncated to zeros I
> discarded. How is the best way of doing this? Do I use match(x,0) /
> (1:length(x))[x==0] ? How do I discard the values as well as wanting the
> original data set values. All suggestions would be greatly appreciated.
>
> Thank you,
>
> James Hutton
>
>         [[alternate HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help

Dear James,

If I understand correctly what you want to do, I can think of several ways 
to do it; here are two:

     > y <- x <- rnorm(20)
     > neg <- x < 0
     > x[neg] <- 0
     > x
     [1] 0.7314066 0.3515410 0.0000000 0.0000000
     [5] 0.0000000 0.0000000 0.0000000 0.0000000
     [9] 0.4341421 0.0000000 0.2766616 0.1823935
     [13] 0.0000000 0.0000000 0.0000000 0.0000000
     [17] 0.0000000 1.3797720 1.2607272 0.6471086
     > x[!neg]
     [1] 0.7314066 0.3515410 0.4341421 0.2766616
     [5] 0.1823935 1.3797720 1.2607272 0.6471086
     > (1:20)[neg]
     [1]  3  4  5  6  7  8 10 13 14 15 16 17
     >
     > neg <- which(y < 0)
     > y[neg] <- 0
     > neg
     [1]  3  4  5  6  7  8 10 13 14 15 16 17
     > y[-neg]
     [1] 0.7314066 0.3515410 0.4341421 0.2766616
     [5] 0.1823935 1.3797720 1.2607272 0.6471086

I hope that this helps,
  John


At 09:32 AM 1/18/2003 -0500, Jmshttn at aol.com wrote:
>Dear Mailing List,
>
>If I wanted a data set of twenty standard normal results, I would type:
>
>x<-rnorm(20)
>
>If I then wanted to make all the negative results in that data set to be
>listed as zero I would then type in:
>
>x[x<0]<-0
>
>However, I now want to discard the values that are zero, but I want to know
>which values out of the original data set which I truncated to zeros I
>discarded. How is the best way of doing this? Do I use match(x,0) /
>(1:length(x))[x==0] ? How do I discard the values as well as wanting the
>original data set values. All suggestions would be greatly appreciated.
>
>Thank you,
>
>James Hutton
>
>         [[alternate HTML version deleted]]
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>http://www.stat.math.ethz.ch/mailman/listinfo/r-help
-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
-----------------------------------------------------