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 > >>> > >>> > >>> > >>> _______________________________________________ > >>> grass-user mailing list > >>> grass-user@lists.osgeo.org > >>> http://lists.osgeo.org/mailman/listinfo/grass-user > >>> > >> _______________________________________________ > >> grass-user mailing list > >> grass-user@lists.osgeo.org > >> http://lists.osgeo.org/mailman/listinfo/grass-user > > > > _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user