[R-sig-Geo] SpatialPolygon with the max value gets no color assigned in spplot function when using "at" parameter

[Roger Bivand]

On Fri, 1 Feb 2013, Jan Hornych wrote:

> Roger,
>
> this is a nice trick, however it works only for small numbers. A large
> double plus a tiny double is the same large double
>
> max(50)==max(50)+.Machine$double.eps
> [1] TRUE
>
> thinking about it now, my question should be. What is the smallest possible
> number that when added to double will make it a different number?

That depends on the size of the number?

> identical(50, (50+(.Machine$double.eps^(1/1))))
[1] TRUE
> identical(50, (50+(.Machine$double.eps^(1/2))))
[1] FALSE
> identical(50, (50+(.Machine$double.eps^(2/3))))
[1] FALSE
> identical(50000, (50000+(.Machine$double.eps^(2/3))))
[1] FALSE
> x <- seq(-50, 50, length.out=100)
> idx <- 1/abs(diff(range(x)))
> min(x)==(min(x) - idx)
[1] FALSE
> max(x)==(max(x) + idx)
[1] FALSE

So some slackening of .Machine$double.eps may help?

Should I add a helper function to classInt and an argument to 
classIntervals() to force [a,b]?

Roger

>
> Thank you
> Jan
>
> On Wed, Jan 30, 2013 at 8:04 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>
>> On Wed, 30 Jan 2013, Jan Hornych wrote:
>>
>>  Hi,
>>> I would like to do coloring of map regions based on the region values
>>> "weight". The approach I am taking is first to break regions into equal
>>> intervals,
>>> classIntervals(spdf$weight,4)$**brks #4 intervals in this case
>>> and than coloring all regions within the interval with the same color
>>> col = brewer.pal(4,"RdYlGn"))
>>> The max "weight" is as well the boundary of the interval The problem is
>>> that the last region is not included into the last interval nad has thus
>>> no
>>> color. I do belive I am missing something, because any other solution to
>>> manually manipulate the intervals, is overcomplicating the simplicity of
>>> classIntervals function.
>>> any idea how to get all rectangles colored?
>>> Thank you
>>> Jan
>>> here is the example, see the rectangle in the right upper corner, it
>>> remains white.
>>> library(sp)
>>> library(classInt)
>>> library(RColorBrewer)
>>> p1=cbind(c(0,0,1,1,0),c(0,1,1,**0,0));colnames(p1)=c("x","y")
>>> p2=cbind(c(0,0,1,1,0),c(1,2,2,**1,1));colnames(p2)=c("x","y")
>>> p3=cbind(c(1,1,2,2,1),c(0,1,1,**0,0));colnames(p3)=c("x","y")
>>> p4=cbind(c(1,1,2,2,1),c(1,2,2,**1,1));colnames(p4)=c("x","y")
>>> p5=cbind(c(2,2,3,3,2),c(0,1,1,**0,0));colnames(p5)=c("x","y")
>>> p6=cbind(c(2,2,3,3,2),c(1,2,2,**1,1));colnames(p6)=c("x","y")
>>> ps1=Polygons(list(Polygon(p1))**, ID="ps1")
>>> ps2=Polygons(list(Polygon(p2))**, ID="ps2")
>>> ps3=Polygons(list(Polygon(p3))**, ID="ps3")
>>> ps4=Polygons(list(Polygon(p4))**, ID="ps4")
>>> ps5=Polygons(list(Polygon(p5))**, ID="ps5")
>>> ps6=Polygons(list(Polygon(p6))**, ID="ps6")
>>> sps = SpatialPolygons(list(ps1,ps2,**ps3, ps4, ps5, ps6))
>>> spdf=
>>> SpatialPolygonsDataFrame(sps,**data.frame(weight=c(0.1,0.1,0.**
>>> 3,0.4,0.45,0.6),row.names=c("**ps1","ps2","ps3","ps4",
>>> "ps5","ps6")))
>>> sp.theme(set = TRUE, regions = list(col = brewer.pal(4,"RdYlGn")))
>>> spplot(spdf, "weight", at=classIntervals(spdf$weight,**4)$brks)
>>>
>>
>> I'm fairly sure I replied to this question very recently, but can't find
>> the link. The at= argument in lattice graphics by default breaks [a, b),
>> see:
>>
>> http://en.wikipedia.org/wiki/**Interval_(mathematics)#**
>> Excluding_the_endpoints<http://en.wikipedia.org/wiki/Interval_(mathematics)#Excluding_the_endpoints>
>>
>> so the upper limit should be eased out beyond the maximum, here doing both
>> for symmetry:
>>
>> ats <- classIntervals(spdf$weight,4)$**brks
>> ats[1] <- ats[1] - .Machine$double.eps
>> ats[length(ats)] <- ats[length(ats)] + .Machine$double.eps
>> spplot(spdf, "weight", at=ats)
>>
>> This is described on the levelplot help page, linked from the spplot help
>> page:
>>
>>       at: A numeric vector giving breakpoints along the range of ?z?.
>>           ...  However, this also means that when supplying ?at?
>>           explicitly, one has to be careful to include values outside
>>           the range of ?z? to ensure that all the data are shown.
>>
>> Hope this clarifies,
>>
>> Roger
>>
>>
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>>>
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>> --
>> Roger Bivand
>> Department of Economics, NHH Norwegian School of Economics,
>> Helleveien 30, N-5045 Bergen, Norway.
>> voice: +47 55 95 93 55; fax +47 55 95 95 43
>> e-mail: Roger.Bivand at nhh.no
>>
>
> 	[[alternative HTML version deleted]]
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no