[GRASS-user] Multiple to one question

[Vincent Bain]

Hmmm, not sure you understood what I suggested (or maybe I did not catch
your point of view !). Let's consider you add two measures a week for
point A (cat=1), and 1 measure monthly for point B (cat=2), then after
one year you have :
* in table1 (cat integer):
2 recors (cat=1 and cat=2)

* in table2 (cat integer, mes float):
116 records (104 records with cat=1 and 12 records with cat=2).

Where is there a problem for you ?
Hope this helps,

VB


Le mardi 14 avril 2009 à 09:38 -0700, Adam Dershowitz, Ph.D., P.E. a
écrit :
> On Apr 14, 2009, at 4:06 AM, Moritz Lennert wrote:
> 
> > On 14/04/09 08:37, Vincent Bain wrote:
> >> Hello Adam,
> >> maybe another solution in this case would be a set of 2 tables :
> >> * one linking to the geometry, that is containing nothing but cat
> >> values,
> >> * another one, containing a cat column (related to the "geometric"
> >> table) and different data columns corresponding to your sampling.
> >
> > I think that if all you want is calculate some means or similar  
> > across dates and then display the results, Vincent's solution is the  
> > easiest.
> >
> > But you could also use layers [1]:
> >
> > layer 1 = January round of sampling
> > layer 2 = February round of sampling
> > etc.
> >
> > You would have to give each point a category value in each layer (cf  
> > v.category) and then either create separate tables for each period  
> > linking each to one of the layers or at least create some obvious  
> > cat values (i.e. 100s for January, 200s for February, etc) and link  
> > on single table to all the layers, but with different cat values in  
> > each layer.
> >
> >
> > Moritz
> >
> > [1] See "Vector object categories and attribute management" on http://grass.osgeo.org/grass64/manuals/html64_user/vectorintro.html 
> >  for a quick introduction
> 
> Thanks,
> 
> But, the problem with both of these approaches, columns, and layers,  
> (Vincent or Moritz version) is that I don't have consistent times for  
> each site.  So, at site A I might have 5 samples, once a month and at  
> site B I have 2 samples, one each year, and site C I have a few spread  
> over a few years.
> So both of those approaches essentially need to have a column, or  
> layer, for each possible time of sampling.  But that is not really  
> appropriate for the quasi-random times of the samples.
> 
> 
> >
> >
> >> Does this help ?
> >> VB
> >> Le lundi 13 avril 2009 à 14:23 -0700, Adam Dershowitz a écrit :
> >>> I am trying to set up a new project in Grass, and I have a  
> >>> question  about the best approach.
> >>> I have different vector locations, and at each one there were  
> >>> multiple  samples taken.  At the moment I have each sample as a  
> >>> row in a data  base.
> >>> My question is how best to put this data into a set of vector  
> >>> points.
> >>> I believe that I can do it in either of two ways (of not others).
> >>> 1)  I can create a vector point at each location, then I think  
> >>> that I  can have multiple cats for that object.  So I think I can  
> >>> do cat=1,3,6  for a given location.
> >>> Will that work OK?
> >>> 2)  I can just create different vector objects, that happen to be  
> >>> at  the identical location, and have each one point to a different  
> >>> cat.
> >>>
> >>> If the above is not clear, here is a bit more detailed example.
> >>> At location A there was a sample collected on 1/1 with a value of  
> >>> 2.1,  on 2/2 with a value of 2.2 and on 3/3 with a value of 3.3
> >>>
> >>> The above data is already 3 rows in a database.
> >>>
> >>> I want to be able to display data about point A (say, average  
> >>> value or  things like that).  Should I just create a vector point  
> >>> A and then do  cat=1,2,3 or should I create 3 different vector  
> >>> points at A, each one  having a different cat?
> >>>
> >>> Any guidance about the benefits or limitations each approach (or  
> >>> any  other approach to consider) would be greatly appreciated.
> >>>
> >>> Thanks,
> >>>
> >>> --Adam
> >>>
> >>>
> >>>
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> >>>
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> 
>