Displaying only points within polygon I created in QGIS

Question

I am trying to map policing activity in NYC for two areas: one area in the Bronx and another in Manhattan.

I want to display ALL of the activity but only WITHIN a couple of square blocks that I am interested in (not the whole precinct - which I have a shapefile for with boundaries already set). My assumption, is that I create a polygon outlining the block areas I want.

But then, how do I attach those boundary coordinates to my CSV database on police activity (that dataset has x y coordinates representing police activity)?

And then, how do I only display the activity within the boundaries rather than all of the activity that exists throughout NYC?

Answer 1

The majority of your problems can be solved with a basic GIS understanding. Therefore i advise you to read some tutorials on the net (for example here on GIS-tutor or click yourself through the QGis Wiki).

Regarding your way of proceeding:

• Load in your point data ( the one with x-y coordinates) as text-delimited file (search for advice on this site or in the tutorials)
• Create your polygons and make a simple spatial join with your points. Alternatively make a subset of your policing activity points to get only those points, which intersect or are contained by your polygons (blocks). You could also create a grid or make a simple join with your data if you stick to the same IDs and names. This entirely depends on what you want to achieve and how you want to display it.

Answer 2

• Use symbolgy and assign the function 'geometry' as below:

pole_of_inaccissibilty($geometry,1)

or

• use the plugin Point sample tools.