This is probably a naive question but I am struggling as a new user to QGIS.
I have a very large shapefile (275,000 points, but can break this into about 10 subregions if necessary for faster processing).
I want to identify all points that have no other point within 200 metres and then code each of those points with the value "unique" in a field of the file.
For all the other points that are part of local clusters I then want to code those as "clustered".
Having achieved that, I want to then select just one for each cluster on a random basis to retain in the data set, discarding the others.
Currently I am failing to achieve step 1 so any assistance would be welcome.