[R] Beginner plot and map questions

[Web User]

Hi,

I have not been able to find answers to these questions in the FAQs, 
manuals, or R-help archives.  If answers are available somewhere, please 
direct me to them.

1.) Is there a way to convert a table (e.g. represented as a data frame) 
to a function, specifying which columns are input and which column is 
output?  It would seem that this would be useful for plotting 
experimental results, since e.g. contour(x, y, f) requires f to be a 
function.

2.) If x is longitude and y is latitude, then I would think that 
contour(x, y, f) could be used to create a contour map with equally 
spaced latitude and longitude.  And I've seen that the "maps" and 
"mapproj" packages can be used to create maps in different projections.
a.) Once a base map is created and experimental data is projected to fit 
the base map, how is it added onto the map?
b.) Is there a way to combine the contouring and projection 
functionality to get contour maps in any of the supported projections?

3.) What algorithm is used by the contour() function?  Are there any 
parameters that can be changed, such as radius of interest for a data 
point to affect a grid point?

Thanks for any help or references.