"Within" for Geo-data - need to place coordinates within geo-areas

[flemmingbj]

Hi!

I have a dataset contaning 1 km squares defined by lat/lon values to show on a map.

I want to summarize values from another dataset for all data that falls within the different squares, eg. the average time for incidents in a specific 1 KM square and then color the squares by measure for a heatmap. 

How do I match latitude and longitude values for my incidents to the square definitions?  I have head of a "within" function, but I can't find anything usable on this.