I have a bunch of points on a map on a river that branches. I want an easy way to select one branch from the other and was hoping I could just somehow "grab" those points on the map and add a column to the attribute table with those points that would delineate the two branches.
Frist of all make an attribute to every single branch; every single branch of the river must be a single polygon's layer feature.
by your question I think you need to do the following steps:
Step 1 Generate a buffer poligon of every branch Qgis~Menù -> Vector -> Geoprocessing Tool -> Buffer. Set "distance" value in a way that you are sure to cover the points around every branch.
Step 2 Use the new buffered polygon layer in a spatial join of the points to add specific attribute Qgis~Menù -> Vector -> Data Management Tools -> Join attribute by location
Set "Input Layer = yourPointsLayer " and set "Join layer = buffered-branch-layer ", use these (check on) geometric predicate: "intersect, touch, are within", select the field to add (for example the field generated on step 1).
NOTE: There are two important settings that are critical in the process
- The buffer size (step 1) must be not too small or too big
- The "join type" setting in spatial join (step 2)
'Select by location'? For instance, there is a related thread How to build a query/expression to select specific points within a buffer in QGIS. Or maybe this article can help you as well Performing Spatial Queries – Taras May 8 '19 at 4:32