[R-sig-Geo] merging tables by columns AND row names (coordinates)

[Michael Sumner]

Hello, I can think of a couple of simple-minded approaches that would 
take some time - either relying on direct string-matching for the unique 
coordinates, or by some contrived overlay.

However, there's probably far better approaches - a couple of questions:

Can you predefine the set of all unique coordinates without reading all 
the tables from file? 
 - if so you might simplify the identification of each individual 
coordinate, for matching the records

Are the coordinates (intended to be) on a regular grid?  (This seems 
unlikely, although it is nearly true given your X coordinates).

Cheers, Mike.


isidora k wrote:
> Hi everyone!
> I have 100 tables of the form:
> XCOORD,YCOORD,OBSERVATION
> 27.47500,42.52641,177
> 27.48788,42.52641,177
> 27.50075,42.52641,179
> 27.51362,42.52641,178
> 27.52650,42.52641,180
> 27.53937,42.52641,178
> 27.55225,42.52641,181
> 27.56512,42.52641,177
> 27.57800,42.52641,181
> 27.59087,42.52641,181
> 27.60375,42.52641,180
> 27.61662,42.52641,181
> ..., ..., ...
> with approximately 1000000 observations for each. All
> these tables have the same xcoord and ycoord and I
> would like to get a table of the form
> XCOORD,YCOORD,OBSERVATION1,OBSERVATION2,... 
> 27.47500,42.52641,177,233,...
> 27.48788,42.52641,177,345,...
> 27.50075,42.52641,179,233,...
> 27.51362,42.52641,178,123,...
> 27.52650,42.52641,180,178,...
> 27.53937,42.52641,178,...,...
> 27.55225,42.52641,181,...
> 27.56512,42.52641,177,...
> 27.57800,42.52641,181,...
> 27.59087,42.52641,181,...
> 27.60375,42.52641,180,...
> 27.61662,42.52641,181,...
> In other words I would like to merge all the tables
> taking into account the common row names of their
> xcoords AND ycoords.
> Not all tables have the same number of observations
> which means that not all pairs of x and y coords
> match.
> Is there a way to do this in R?
> I would be grateful for any advice.
> Many thanks
> Isidora
>
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