[R-sig-Geo] spplot: labels on maps / variables on different scales

[Michael Friendly]

Edzer Pebesma wrote:
>
>
> Michael Friendly wrote:
>> Two short questions about working with maps:
>>
>> 1.  I'm reading a shapefile with character labels for the regions 
>> (FSA).  I can add the labels using plot(),
>> but when I try the same thing using spplot(), the labels are in the 
>> wrong positions -- they all seem to be
>> shrunk somewhat in toward the center of the map.  What am I doing wrong?
>>
>> # this doesn't work-- labels in wrong position
>> spplot(toronto,"FSA_NAME", colorkey=FALSE)
>> text(coordinates(toronto), labels=as.character(toronto$FSA), cex=0.4)
> Right: text() works with base graphics, not with lattice on which 
> spplot is built.
>
> Something like this should work:
> spplot(toronto,"FSA_NAME", colorkey=FALSE,
>    sp.layout = list("sp.text", coordinates(toronto), 
> as.character(toronto$FSA), cex=0.4))
>
Great!  Now I also know where to look to generalize this.
>>
>> 2. I have a bunch of attribute variables for the geographic regions, 
>> all on different scales.  Id like to
>> produce a set of comparative maps in the same figure (say with 
>> spplot()) with each attribute shaded
>> by its quantiles, e.g., 5 classes each.  Do I have to precompute 
>> these first, or is there something I can do in the call
>> to spplot() to have this done, using the variables in the 
>> SpatialPolygonsDataFrame?
> What exactly did you mean by "all on different scales"? They have 
> different polygon structures?
No - some of the attribute values are percents, some are quantitative & 
positively skewed, like Income. If I do

spplot(toronto, c("Household.Income","Unemployed","University"))
a single scale is applied to all three, so the two % variables are 
shaded uniformly in the lowest range.
What I'd like is to apply a function to take each of these and recode 
into quantiles for that variable.

It's partly that my data variables are now in the map object and, from 
the help, I only know how to refer to
zcol= names of these, rather than some transformations on the underlying 
data.

-- 
Michael Friendly     Email: friendly AT yorku DOT ca 
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street    http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT  M3J 1P3 CANADA