[R-sig-Geo] Map2points() substitute for class "map"

[Fernando Mayer]

Dear Roger, thank you very much again for your help. I didn't know 
about PBSmapping and the Rgshhs() function. It seems both will be very 
useful to me.

Thanks again,
Fernando Mayer.

Roger Bivand escreveu:
> On Mon, 12 Feb 2007, Roger Bivand wrote:
> 
>> On Mon, 12 Feb 2007, Fernando Mayer wrote:
>>
>>> Roger, thanks for your explanations. Thanks also to Edzer Pebesma who 
>>> provided soma additional improvements. However, now I think I have 2 
>>> problems, as follows:
>>>
>>> Roger Bivand escreveu:
>>>
>>>> If you comment out the lines:
>>>>
>>>> #  if(missing(map)) stop("map object is missing.")
>>>> #  if(!inherits(map, "Map")) stop("Map.obj must be of class Map")
>>>> #  if(missing(variable)) stop("variable to be plot is missing")
>>>>
>>>> in ProportionalSymbolMap(), and rename the map argument as verts, you can 
>>>> pass the coordinates in:
>>>>
>>>> library(maps)
>>>> map <- map("county", "illinois", fill=TRUE, col="transparent", plot=FALSE)
>>>> library(maptools)
>>>> str(map)
>>>> ID <- substring(map$names, 10)
>>>> ill <- map2SpatialPolygons(map, ID, proj4string=CRS("+proj=longlat"))
>>>> plot(ill, axes=TRUE)
>>>> x <- runif(102)
>>>> ProportionalSymbolMap_rev(coordinates(ill), x, max.size=0.3)
>>> # Problem 1
>>>
>>> Doing exactly this, I have an error in
>>>
>>>  > plot(ill, axes=TRUE)
>>> Error in as.vector(x, "double") : cannot coerce to vector
>>>
>>> and I was not able to find out what is going wrong. However if I do
>>>
>>>  > map("county", "illinois", fill=TRUE, col="transparent", plot=T)
>>>
>>> before all that code code and ignore the error, I can see the map with 
>>> the proportional symbols. So I don't know exactly how long this error 
>>> influence on what was to be the point here. But, I understood 
>>> something new here and know comes the
>> At a distance it's difficult to say - but from #2 below, it doesn't 
>> matter, because the map is only a background, it does nothing itself.
>>
>>> # Problem 2
>>>
>>> As far as I could understand, the polygon IDs are used to identify 
>>> where the symbols are to be plotted (after the processment with 
>>> map2SpatialPolygons()). Maybe it was my mistake haven't said this 
>>> before, but what I'm trying to do is to plot the symbols not in the 
>>> land, but in the ocean. So I think there's no polygon IDs in this case 
>>> isn't?
>> Well, using map() to access boundary data is usually to attach data to the
>> polygons, but your case is different, you only need a background. My first
>> idea would be to see whether the PBSmapping package already has what you
>> need - they are Northern Pacific, but that doesn't have to hurt for your
>> South Atlantic location. 
>>
>> I think that I would try to get the coastlines you need from map() or
>> Rgshhs() in maptools (possibly with a higher resolution GSHHS database),
>> and convert them to a PBSmapping object. The reason for suggesting
>> PBSmapping is that the functions provided there are for fisheries
>> research, and so may be closer to you than more general functions.
>>
>> library(maptools)
>> gshhs.c.b <- system.file("share/gshhs_c.b", package="maptools")
>> SA <- Rgshhs(gshhs.c.b, xlim=c(295,340), ylim=c(-10,-55))$SP
> 
> Of course:
> 
> SA <- Rgshhs(gshhs.c.b, xlim=c(295,340), ylim=c(-55, -10))$SP
> 
> Sorry!
> 
>> plot(SA, axes=TRUE, col="grey")
>> SA_PBS <- SpatialPolygons2PolySet(SA)
>> plotMap(SA_PBS)
>>
>> I found the map on page 19 of their User Guide quite like what you are 
>> after, but they choose to colour-fill the quadrats.
>>  
>> The same things can be done with generic sp class objects too.
>>
>> Roger
>>
>>> What I'm trying to do exactly is maps to plot fishery data, with the 
>>> symbols proportional to catch, effort, etc. I was trying something 
>>> like this [1], which is a function using map(), degAxis(), quantile(), 
>>> points(), legend(), etc. However I would like to improve this, mainly 
>>> the legend and the way the symbols are plotted. That's why I was 
>>> trying the ProportionalSymbolMap(). But now, because of the polygon 
>>> IDs I'm not sure anymore how this could be done.
>>>
>>> [1] http://img468.imageshack.us/img468/9397/rplot005us9.png
>>>
>>> Thanks again for the explanations,
>>>
>>
> 

-- 
Fernando Mayer
Grupo de Estudos Pesqueiros - GEP
Centro de Ciências Tecnológicas, da Terra e do Mar - CTTMar
Universidade do Vale do Itajaí - UNIVALI
Itajaí - SC - Brasil
e-mail: fernandomayer [@] gmail.com