Sunday, 31 May 2015

qgis - Spatial join without operation on the variable of interest


I have a simple problem: I've got to spatially join records of an epidemic in forests to some plot coordinates I have gathered. Problem is, I cannot obtain the records for each year on each plot, I can either get the first record for each plot (not enough, since it's only one year) or get all those records but only after they've been transformed through either mean, min, max, median operation through the attribute summary choice I make, resulting in a single line but with data I can't exploit for my work.


I'd rather have duplicates of my rows (each corresponding to the state of the plot for a given year) so I can analyse the epidemic data year by year.



I am a first time user of QGIS: my data is stored in shapefiles, all of it (I created one out of my plot coordinates for a simple Excel sheet, and the rest was downloaded from here directly, shapefiles as well: http://www.donnees.gouv.qc.ca/?node=/donnees-details&id=2eed323f-e3fd-40cf-98c4-d0d25c52c404#meta_telechargement ; it's in French)



Answer



It's a one-to-many relationship. Do an intersect instead. If you really want to keep the non relating records, use the ArcToolBox Spatial Join tool with the JOIN_ONE_TO_MANY option.


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