Re: [R] "spreading out" a numeric vector

From: Greg Snow <Greg.Snow_at_imail.org>
Date: Mon, 24 Mar 2008 10:43:51 -0600

Levi,

Here is one possible function:

spread <- function(x, mindiff) {
  df <- x[-1] - x[-length(x)]
  i <- 1
  while (any(df < mindiff)) {
    x[c(df < mindiff, FALSE)] <- x[c(df < mindiff, FALSE)] - mindiff/10     x[c(FALSE, df < mindiff)] <- x[c(FALSE, df < mindiff)] + mindiff/10     df <- x[-1] - x[-length(x)]
    i <- i + 1
    if (i > 100) {

       break
    }
  }
  x
}

I have tried experimenting with using optim to minimize a function of the distances between new points and old points penealized for being to close, but it sometimes gave me some weird results, the above has worked fairly well for me (the above is based on some of the code inside the triplot function in the TeachingDemos package).

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow_at_imail.org
(801) 408-8111
 
 


> -----Original Message-----
> From: r-help-bounces_at_r-project.org
> [mailto:r-help-bounces_at_r-project.org] On Behalf Of Levi Waldron
> Sent: Saturday, March 22, 2008 7:03 PM
> To: R-help mailing list
> Subject: [R] "spreading out" a numeric vector
>
> I am creating a timeline plot, but running into a problem in
> positions where the values to plot are too close together to
> print the text without overlap. The simplest way I can think
> of to solve this (although there may be other ways?) is to
> create a new numeric vector whose values are as close as
> possible to the original vector, but spread out to a given
> minimum difference. For example, take the following vector:
>
> > x <- c(1,2,seq(2.1,2.3,0.1),3,4)
> > x
> [1] 1.0 2.0 2.1 2.2 2.3 3.0 4.0
> >
>
> However, suppose I don't want to plot any of these points
> with less than 0.5 between them. The problem could be solved
> by a function that behaved something like this:
>
> > x2 <- spread(x,mindiff=0.5)
> > x2
> [1] 0.5 1.0 1.5 2.0 2.5 3.0 4.0
>
> Or for a minimum difference of 0.2,
> > x2 <- spread(x,mindiff=0.2)
> > x2
> [1] 1.0 1.8 2.0 2.2 2.4 3.0 4.0
>
> Thus, if there is a cluster of close values, spreading the
> values may require changing values which previously weren't
> too close to their nearest neighbors.
>
> Then I could use segments() to draw lines from the timeline
> to where the shifted text is printed, labeling tics on the
> timeline accurately but keeping the text from overlapping.
>
> Any ideas on how to program this or how to do it using
> built-in functions would be greatly appreciated.
>
> ______________________________________________
> R-help_at_r-project.org mailing list
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>
______________________________________________ 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.
Received on Mon 24 Mar 2008 - 16:54:43 GMT

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