[R-sig-Geo] Changing color ramp in spplot()

[Edzer Pebesma]

Aleksey Naumov wrote:
> Edzer,
> 
> Thank you for your help. I did overlook col.regions argument in spplot.
> However, in trying to trace down the exact meaning of this argument, I could
> not find it in either xyplot() or it's panel function panel.xyplot(), which,
> as you indicated, would be used in this case (since we are plotting points).
> Instead, I found col.regions in panel.levelplot; so is panel.levelplot()
> used in this case, even though we are not plotting areas?

no, for points spplot maps its col.regions argument to a col argument it
passes on to xyplot. Also, it has its own panel function, you see it by

sp:::panel.pointsplot

> 
> The following syntax works for me:
>> spplot(meuse, "zinc", col.regions=colorRampPalette(c('blue', 'gray80',
> 'red'))(5))
> 
> but it requires that I specify the number of colors explicitly (5 in this
> case). Is there a way to specify just a palette function, and the number of
> colors would be figured out automatically by lattice? Simply providing the
> palette function like colorRampPalette or cm.colors does not work:
>> spplot(meuse, "zinc", cuts=7, col.regions=cm.colors)
> Error in col.regions[cols] : object of type 'closure' is not subsettable

no, you need to pass colors, not a color palette generating function.

> 
> Thank you,
> Aleksey
> 
> 
> 
> On Fri, Mar 19, 2010 at 11:04 AM, Edzer Pebesma <
> edzer.pebesma at uni-muenster.de> wrote:
> 
>> Aleksey,
>>
>> It seems you missed the documentation of ?spplot, or misunderstood. It
>> describes a col.regions argument, which accepts a color ramp.
>>
>> spplot is a relatively thin wrapper around the functions xyplot (for
>> points or lines) or levelplot (for areas) in package lattice. If you
>> want to do all kind of fancy things, you might want to have a look at
>> their documentation.
>>
>> Best regards,
>>
>> Aleksey Naumov wrote:
>>> Dear R experts,
>>>
>>> I am new to using the "sp" package and I am wondering how does one change
>>> color palette in spplot()? The problem is that when I do:
>>>> library(sp)
>>>> data(meuse)
>>>> coordinates(meuse) = c("x","y")
>>>> spplot(meuse, "zinc")
>>> the middle class (zinc concentrations (803.4, 1149]) is plotted in white
>> and
>>> is therefore not visible on the graph. I guess this is due to the default
>>> cyan-magenta color palette used in "lattice". I tried changing the colors
>>> via (a) manipulating the lattice settings, and (b) arguments to spplot,
>> but
>>> could not get it to work. How does one go about changing the default
>> color
>>> ramp?
>>>
>>> I also tried using the "panel" argument to extend the default
>>> panel.pointsplot panel function used here, to make sure that all points
>> are
>>> visible (perhaps, as open circles, which are then filled in by
>>> panel.pointsplot), but could not figure out how to do it right.
>>>
>>> Would appreciate any ideas.
>>>
>>> Thank you,
>>> Aleksey
>>>
>>>       [[alternative HTML version deleted]]
>>>
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>> --
>> Edzer Pebesma
>> Institute for Geoinformatics (ifgi), University of Münster
>> Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
>> 8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
>> http://www.52north.org/geostatistics      e.pebesma at wwu.de
>>
> 

-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics      e.pebesma at wwu.de