[R-sig-Geo] Better print method for Spatial*DataFrames?

[Roger Bivand]

On Fri, 28 May 2010, Barry Rowlingson wrote:

> On Fri, May 28, 2010 at 5:18 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>> On Fri, 28 May 2010, Etienne Bellemare Racine wrote:
>>
>>> I taught I could add my two cents.
>>>>
>>>> Nice suggestion!
>>>
>>> I agree !
>>
>> No. Only for SpatialPointDataFrame objects, which is what it does already.
>> Please, understand that str() is a *much* better choice in effectively all
>> cases where summary() isn't used. For the Spatial* objects, set a
>> max.level=2 or similar, and you can *see* what is in it. The proposed
>> print() method for a big multiband raster will also run away with you. Do
>> str(), not print()!!!
>
> I'm not sure what you're saying 'No' to here, Roger. Neither str(xx)
> nor summary(xx) present the object as a data frame. Conceptually its a
> data frame where one of the columns is a geometry, and seeing it print
> as such is a good thing (imho). I'd like to never have to use xx at data
> again!

Just pragmatics, since things which have rushed off the top of my screen 
really are not much help, I find.

I use as(xx, "data.frame") when needed, but most often subset both 
observations and variables by "[". I'm not sure where displaying all the 
data gets you for more than a trivial number of observations and 
variables, though? The output will still swamp the console/terminal 
buffer. I'm thinking of a multi-band raster, but even standard 
show(meuse.grid) as a data.frame only leaves rows 2605-3103 on screen for 
a standard gnome-terminal. The data editor I see doesn't have a scroll 
bar, so to scroll, one would need an external viewer, I think.

In other software systems (octave, Stata, ...), one can turn on and off a 
more/less screen-by-screen displayer (not scrolling upwards, just 
chunking), but I'm not aware of an equivalent in R/S. I'm not sure how 
head() and tail() work in R, and personally use str() by default. If I 
need to access the coordinates of a particular line or polygon, I print() 
just that list element (Line or Polygon object).

I can see what you mean, but feel that users will benefit much more by 
using str(), which is a real gem!

Roger

>
> I'm not sure trying to truncate the coordinates for nice formatting
> is a good idea though, but some indication when printing a
> Spatial*DataFrame that its a dataframe with geometries seems a good
> idea.
>
> Barry
>

-- 
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