[R] Automatic routine - NEW
Spencer Graves
spencer.graves at pdf.com
Wed Jun 23 15:46:14 CEST 2004
The documentation is good for things like this. In most (all recent?)
versions of R, "help.start()" brings up a help page. Select "An
Introduction to R", and go to "Vector Indices". Also look at "Arrays and
Matrices: Array Indexing". There, you will find that "DF[3:5,]" might be
what you want.
Actually, I'm not certain that your "c" below is what you want, because
class(c[1,1]) is "list", and I could not do arithmetic on it. I
discovered that when I tried all.equal(c, DF[3:5,]). {Also, "c" is the
name of a very useful function; try "?c". It is usually wise to avoid
using names of functions for matrices of data.frames. R will select the
one you want from the context in most but not all cases.}
hope this helps.
spencer graves
Monica Palaseanu-Lovejoy wrote:
>Hi Again,
>
>First of all thank you for all the responses to my previous query.
>Your answers were very helpful and I did the job ;-). Now I hope you
>can answer as quick the following (sorry I am invading you with
>trivial questions):
>
>Let’s use again the following data.frame example:
>DF <- data.frame(x=rnorm(5), y=rnorm(5))
>
>I want to obtain a new data.frame (or matrix) that contains only n
>rows (from the i rows DF has), and all the columns. If I have to do it
>step by step I would do something like that, for example:
>
>a3 <- DF[3,]
>a4 <- DF[4,]
>a5 <- DF[5,]
>b <- data.frame(a3, a4, a5)
>c <- matrix(b, nrow=3, ncol=2, byrow=TRUE)
>
>Now I want to do the same in one go, so I wrote:
>
>for (i in 3:5)
>{
> d[i] <- DF[i,]
> e <- data.frame(d[i])
> f <- matrix(e, ncol=2, nrow=3, byrow=TRUE)
>}
>
>Which of course gives me errors and the matrix f has all elements
>equal with DF[5,5]. If I don’t use [i] after d, the resulting f matrix is
>made up from the DF[5,] elements (which is quite normal since i
>replaces itself ...). So ..... How is this done correctly?
>
>I am really appreciating your time and effort to answer me,
>
>Monica
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>
>
More information about the R-help
mailing list