qgis
I am a beginner with QGIS. What I need to do is take a group of zipcodes and group them together (create a territory) in a way that is recorded in an underlying database.
Ideally, I would like to highlight a group of zipcodes and assign a value to them as an attribute (column) in the underlying layer file (database).
Anyone know if that can be done in the mapping software?
Starting from QGIS 2.2 this is supported in a very natural way. It can be done via the QGIS expression engine using the QgsFeatureRequest.setFilterExpression( unicode ) method.
# The important part: get the feature iterator with an expression
it = l.getFeatures( QgsFeatureRequest().setFilterExpression ( u'"Counties" = \'Norwich\'' ) )
# Set the selection
l.setSelectedFeatures( [ f.id() for f in it ] )
The best thing about it: if you have a recent QGIS version (2.10 and later), this will be filtered directly in the database so much more performant than other solutions while still being very readable.
You can get rather close with OpenJUMP
Select the layer that covers your research area.
Create a grid with desired spacing as line grid, polygon grid, or point grid.
Grid features will have one attribute that is a combination of X and Y coordinates. If you want a rotated grid make the grid layer editable, select all features and use the Rotate Selected Item tool.
Result is not perfect when it comes to labels. Perhaps it is possible to create a new attribute that is better for labeling by using some attribute calculator tool.
Best Answer
Select features you want to group. Right click your zip code feature class in the Layers Panel. Open Attribute Table. Click on the pencil icon in the top left corner to start an edit mode. Click the field calculator (last icon on right) and "Click update existing field" if you have one to store the grouping values or choose to "create a new field" if you don't. Type in value for grouping in the expression box, make sure Only update # selected features is checked. Continue this process until all the polygons have their group values. Stop and save edits. Close attribute table.
Go to Vector menu at top of screen->Geoprocessing Tools->Dissolve. Choose the feature class you just edited as the input and select the field you based your grouping on for the Dissolve field. That should do it.