[R] Coloring counties on a full US map based on a certain criterion

[Ray Brownrigg]

On 14/01/2012 10:33 a.m., Dimitri Liakhovitski wrote:
> Somewhat related question out of curiousity:
> Does anyone know how often the list of the counties and county names
> is updated in this package? Or is it done "centrally" for all packages
> that deal with US counties?
> Thanks!
> Dimitri
>
Well, I would hazard a guess that the package maintainer would know :-)

The answer to your first question is "As and when the package maintainer 
is informed of errors or changes".

The answer to your second question is "No."

Ray
> On Fri, Jan 13, 2012 at 3:41 PM, Ray Brownrigg
> <Ray.Brownrigg at ecs.vuw.ac.nz>  wrote:
>> On 14/01/2012 8:04 a.m., Sarah Goslee wrote:
>>> On Fri, Jan 13, 2012 at 1:52 PM, Dimitri Liakhovitski
>>> <dimitri.liakhovitski at gmail.com>    wrote:
>>>> Just to clarify, according to help about the "fill" argument:
>>>> logical flag that says whether to draw lines or fill areas. If FALSE,
>>>> the lines bounding each region will be drawn (but only once, for
>>>> interior lines). If TRUE, each region will be filled using colors from
>>>> the col = argument, and bounding lines will not be drawn.
>>>> We have fill=TRUE - so why are the county borders still drawn?
>>>> Thank you!
>>>> Dimitri
>>>>
>>> This prompted me to check the code:
>>>
>>> if fill=TRUE, map() calls polygon()
>>> if fill=FALSE, map() calls lines()
>>>
>>> But polygon() draws borders by default.
>>>> plot(c(0,1), c(0,1), type="n")
>>>> polygon(c(0,0,1,1), c(0,1,1,0), col="yellow")
>>> To not draw borders, the border argument is provided:
>>>> plot(c(0,1), c(0,1), type="n")
>>>> polygon(c(0,0,1,1), c(0,1,1,0), col="yellow", border=NA)
>>> But that fails in map():
>>>> map('county', 'iowa', fill=TRUE, col=rainbow(20), border=NA)
>>> Error in par(pin = p) :
>>>    invalid value specified for graphical parameter "pin"
>>>
>>> because border is used as a named argument in map() already, for setting
>>> the
>>> size of the plot area, so there's no way to alter the border argument
>>> to polygon.
>>>
>> Coincidentally, I became aware of this just recently.  When the maps package
>> was created (way back in the "'new' S" era), polygon() didn't add borders,
>> and that is why ?map states that fill does not add borders.  A workaround is
>> to change the map() option border= to myborder= (it is then used twice in
>> map()).
>>
>>> The work-around I suggested previous (lty=0) seems to be the only
>>> way to deal with the problem.
>>>
>> In fact I believe there is another workaround if you don't want to modify
>> the code; use the option resolution=0 in the map() call. I.e. try (in
>> Sarah's original Iowa example):
>>
>> map('county', 'iowa', fill= TRUE, col = classcolors[countycol],
>> resolution=0, lty=0)
>>
>> This ensures that the polygon boundaries match up.
>>
>> I'll fix the border issue in the next version of maps (*not* the one just
>> uploaded to CRAN, which was to add Cibola County to NM).
>>
>> Ray Brownrigg
>>> Sarah
>>
>
>