[R-sig-Geo] Mapping multiple attributes at once

[Pierre Roudier]

Hello Thiago,

First, I owe you and the list a reproducible example (my first example
does not run properly - my bad):

dat <- data.frame(x=runif(50), y=runif(50),
category=sample(letters[1:3], size=50, replace=TRUE),
continuous=runif(50))
# You may want to do some spatial analysis on that data.frame
library(sp)
coordinates(dat) <- ~x+y
# Some spatial analysis here

# Now you want to plot it
library(ggplot2)
df <- as.data.frame(dat) # backtransforms dat into a data.frame object
(ggplot2 does not handle sp objects)
# Here I chose to plot the continuous variable with the size of the
bubbles, and the categorical variable with the colours
my.plot <- ggplot(data=df, aes(x=x, y=y)) +
geom_point(aes(size=continuous, colour=category)) + coord-equal()
print(my.plot)

Second, about plotting a shape file: yes, it is possible. Consider
this blog entry for example:
http://blog.revolutionanalytics.com/2009/11/choropleth-challenge-result.html

Basically, you want to use either geom_path() for simple state
boundaries, or geom_polygon() for polygons (e.g. you want to map some
attribute by state).

Sorry I haven't much experience with this. That could be a good
question on the ggplot2 mailing list
(http://groups.google.com/group/ggplot2).

Pierre


2010/8/25 Thiago Veloso <thi_veloso at yahoo.com.br>:
>   Hello, Matthew.
>   Just a superb complement of yours.
>   I was about to ask the same question to Pierre and Paul, after thanking them for the useful and functional tip. I managed to follow the ggplot examples, but a next step would involve plotting my interest points over a shape file (state contour).
>   Is that possible?
>   Best wishes,
>   Thiago.
>
> --- On Tue, 24/8/10, Matthew Landis <landis at isciences.com> wrote:
>
> From: Matthew Landis <landis at isciences.com>
> Subject: Re: [R-sig-Geo] Mapping multiple attributes at once
> To: r-sig-geo at stat.math.ethz.ch
> Date: Tuesday, 24 August, 2010, 11:47
>
>  I've been following this topic with some interest, since this is something I might like to do fairly often.  I'm not that familiar with ggplot2, but it looks really useful.  Is there a way to overplot (or underplot) a shapefile (e.g. of coastlines) with the approach suggested by Paul?
>
> Matt
>
> On 8/24/2010 10:25 AM, Paul Hiemstra wrote:
>> In addition to the reply by Pierre Roudier, take a look at the ggplot2
>> pacakge. An example:
>>
>
>
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