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

[Mikkel Grum]

merge(Table1, Table2, 
   by = intersect(c("XCOORD", "YCOORD"), 
   c("XCOORD", "YCOORD")), all = TRUE)

It might not handle the amount of data you have, but,
if your tables are normal dataframes, it would do the
job with a smaller dataset. It doesn't work with
Spatial*DataFrames (yet?).

Mikkel

--- Roger Bivand <Roger.Bivand at nhh.no> wrote:

> On Fri, 8 Sep 2006, Michael Sumner wrote:
> 
> > 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).
> 
> The key question is what the data are. To me they
> look like a global 
> regular grid with some slippage in the print() - the
> underlying diff() of 
> the unique x's and y's is almost certainly regular.
> I'm not sure why they 
> are in text files either (model output?). But some
> bits of the grid may be 
> missing, the question being whether this is regular.
> If as an earlier 
> response indicated different data sets have
> different grid cells 
> missing, then we need the overall grid to start
> with, then grab the row 
> and column indices (and/or grid index), and attach
> these to the data rows. 
> 
> If the solution needs to be robust, and have a
> longer term utility, I 
> would go for using MySQL, Terralib, and aRT. The
> data representation is 
> that of the Terralib Cell object, so the question
> would be how to upload 
> to the database from the text files.
> 
> aRT is at:
> 
> http://www.est.ufpr.br/aRT/
> 
> By the way, 1M by 100 by 8 bytes is pushing 32-bit R
> - but handing off a 
> lot of the data storage to a database relieves this
> greatly.
> 
> Roger
> 
> > 
> > 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
> > >
> > > _______________________________________________
> > > R-sig-Geo mailing list
> > > R-sig-Geo at stat.math.ethz.ch
> > > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> > >
> > >
> > >
> > 
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> > 
> 
> -- 
> Roger Bivand
> Economic Geography Section, Department of Economics,
> Norwegian School of
> Economics and Business Administration, Helleveien
> 30, N-5045 Bergen,
> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
> e-mail: Roger.Bivand at nhh.no
> 
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