[R-sig-Geo] mapping introduction

[Dylan Beaudette]

On Saturday 24 November 2007 08:31:33 pm tom sgouros wrote:
> Thanks very much for the reply.  I think a lot of my confusion is in not
> knowing where the boundaries fall between the different applications.
> Can you tell me roughly the division of labor among the software you
> mentioned?

Sure. I use GRASS / PostGIS anytime I need to work with GIS data: raster, 
vector + attributes, etc. Importing, merging, subsetting, modification, and 
summarizing are best done within a GIS (I think). When I need graphical 
summaries (box and whisker plots and such) I will import the data into R and 
go from there. In other words, most of the heavy lifting of pushing pixels 
and vertices is done in the GIS. All of the analysis is done in R: summaries, 
hypothesis testing, and prediction using models. This nice thing about the 
GRASS-R bindings is that you can predict from GRASS data, and send the 
predicted values right back into a GRASS raster/vector . 

Lately I have been using R to produce some maps -- although mainly maps of 
purely vector data like thematic maps. The high quality PDF output from R 
makes for an ideal platform for producing press-ready vector graphics. Check 
out the spplot() function in the sp package for plotting a mixture of 
vector / raster data. When plotting raster data out to a PDF, be careful 
about generating gigantic files -- each pixel can be represented with a 
little rectangle, and for large grids can result in massive PDF files. 

I will try and post an examples of this.. in the mean time check out Roger's 
sp website- it should be in the manual page for the sp package. There are 
numerous mapping examples in there. 

For more complex maps I tend to favor GMT. Examples:
http://casoilresource.lawr.ucdavis.edu/drupal/node/130

>
> Dylan Beaudette <dylan.beaudette at gmail.com> wrote:
> > For most of my work GRASS,
> > GMT, PostGIS, R, and Mapserver are a tough combination to beat.
>
> Do you know any identifying details about the books you speak of here?
> (Are you writing one?)

I had to look through some notes: i am reviewing one of them, and contributed 
a chapter (along with Markus Neteler and others) to the other. 

1. Desktop GIS by Gary E. Sherman
This one provides an excellent introduction to both GIS and the entire range 
of open source software which can be used. There isn't (as of now) anything 
in there about R, but is a great resource otherwise.

2.  G.B. Hall (Ed), "Open Source Approaches to Spatial Data Handling", 
Springer, New York. In press.

This one should have some material on R -- sprinkled into some of the relevant 
chapters. I know that the GRASS chapter has a bit on R, specifically that 
kriging example I sent last time. 

A Related example can be found here:
http://casoilresource.lawr.ucdavis.edu/drupal/node/442


Those books should be out soon- I will post back when I hear from the 
authors / publisher.

> > See above suggestions. There should be two books out soon which are
> > dedicated to opensource GIS applications- I would keep an eye out for
> > these.
>
> Thanks again,
>
>  -Tom

Cheers,

Dylan