[R] Fwd: Re: Creating "Envelope" around a plot

[Jim Lemon]

Hi Nick,
I don't think it will do all that you have described, but the "dispersion"
function in the plotrix package will draw an "envelope" around a line if
you specify type="l" and fill=<some_color>. If you pass ulim=<some_value>,
the "envelope" will extend that far from the original line. See the second
example on the help page to overplot the original line.

Jim


On Tue, Nov 3, 2015 at 4:35 AM, William Dunlap <wdunlap at tibco.com> wrote:

> > summing the Euclidean distances between points in the strands
> > ... if two one strand lies within the "envelope" of another I can set
> them together
>
> Use the max instead of the sum.
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Mon, Nov 2, 2015 at 9:29 AM, WRAY NICHOLAS <nicholas.wray at ntlworld.com>
> wrote:
>
> > Hi Bill I have been doing exactly that, ie summing the Euclidean
> distances
> > between points in the strands   Although with small sets of strands this
> > technique allows me to group the strands into various sets, which I can
> > assume are the same, unfortunately once I have a larger number of strands
> > the distances between groups become on the same order as the distances
> > within groups as so it's no longer clear cut.  I have tried various
> > approaches, include a kind of Monte Carlo sampling to create the distinct
> > groups but the best approach seems to be a kind of "kinship" idea, where
> if
> > two one strand lies within the "envelope" of another I can set them
> > together.  But as said, creating the envelope in R is not straightforward
> >
> > Thanks Nick
> >
> > On 02 November 2015 at 16:51 William Dunlap <wdunlap at tibco.com> wrote:
> >
> > Instead of computing the envelopes (of various radii) of paths and seeing
> > if they intersect
> > you could compute distances between paths and seeing if they are smaller
> > than a given
> > distance. Computing the distance between 2 polylines is not difficult,
> > although computing
> > it quickly for very long sequences of line segments is more difficult.
> >
> > Bill Dunlap
> > TIBCO Software
> > wdunlap tibco.com
> >
> > On Mon, Nov 2, 2015 at 7:19 AM, WRAY NICHOLAS <
> nicholas.wray at ntlworld.com>
> > wrote:
> >
> >
> > > ---------- Original Message ----------
> > > From: WRAY NICHOLAS < nicholas.wray at ntlworld.com>
> > > To: Duncan Murdoch < murdoch.duncan at gmail.com>, r-help
> > > <r-help at missing_domain>
> > > Date: at
> > > Subject: Re: [R] Creating "Envelope" around a plot
> > >
> > >
> > > Hi Dennis again, I see what you're getting at and it looks rather
> groovy
> > > but unfortunately what I actually need is the vector of the points on
> > the
> > > boundary (the graphics just being a way of checking that everything's
> as
> > it
> > > should be) and so it rather looks like I need to do a lot of
> calculating
> > of
> > > orthogonal vectors along straight stretches and circles round peaks
> > >
> > > I'm looking to do an algorithmic filtration of strands which lie within
> > > the "envelope" of other strands -- your method would allow visual "by
> > hand"
> > > inspection but unfortunately I've got hundreds of strands to compare!
> > >
> > > But thanks again -- useful thoughts Nick
> > >
> > > > >
> > > > On 02 November 2015 at 15:03 Duncan Murdoch
> > > > < murdoch.duncan at gmail.com> wrote:
> > > >
> > > >
> > > > On 02/11/2015 7:33 AM, WRAY NICHOLAS wrote:
> > > > > Hi I am plotting various strands of information, and I want to
> > > > > create an
> > > > > "envelope" around each line, so that the locus of the envelope is
> > > > > the boundary
> > > > > points no more than a fixed maximum distance from the plotted
> > > > > line, a bit like
> > > > > drawing a larger rectangle with paralle sides and curved compass
> > > > > corners around
> > > > > a smaller rectangle. Obviously I can work out how to do this in
> > > > > code
> > > > > (eventually) but I suspect it would take me a while and i was
> > > > > wondering whether
> > > > > there was some R function which I don't know about which creates
> > > > > sets of of
> > > > > points at a given maximal distance
> > > > >
> > > > > the lines are simple vectors, ie like this noddy example
> > > > >
> > > > > veca<-c(4,3,6,5,7,3,2,3,3,6,8,7)
> > > > > plot(veca,type="l",lwd=2)
> > > > >
> > > > > then I want to plot the locus of the boundary of all points no
> > > > > more than (say) 1
> > > > > unit from the line I imagine that one would have to provide a
> > > > > larger set of
> > > > > interpolated points between the actual points of veca, but I can
> > > > > do that no
> > > > > problem
> > > > >
> > > > > I'd be grateful if anyone out there in the R-ethervoid has any
> > > > > ideas
> > > >
> > > > The graphics system will do this for you automatically if your
> > > > coordinate system has the same scale in x and y, and you use a
> > > > really
> > > > huge line width. For example,
> > > >
> > > > veca<-c(4,3,6,5,7,3,2,3,3,6,8,7)plot(veca, lwd=150, col="gray",
> > > > type="l")lines(veca, lwd=2)
> > > >
> > > >
> > > > If you want to be 1 unit away in user coordinates and the x and y
> > > > scales
> > > > are different, it will be a lot harder.
> > > >
> > > > Duncan Murdoch
> > > >
> > > > >
> > > >
> > >
> >
> >
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
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> > and provide commented, minimal, self-contained, reproducible code.
> >
> >
> >
> >
> >
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
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