I have a points layer with a frequency field indicating a population at that point. There is also a field indicating the broader area by which I need to analysis broken down into. I am expecting the points to be mostly grouped in a number of clusters. I need a way of determining how many clusters there are, probably by density, and to return a point for the centre of each. I've made a heatmap in the display section of the points layer by setting a radius and weighting by the frequency field and in this created three clusters in my trial area, that look right, but I don't see how to get a coordinate for them. Any suggestions of what tool(s) to look at.

I have a points layer with a frequency field indicating a population at that point. There is also a field indicating the broader area by which I need to analysis broken down into. I am expecting the points to be mostly grouped in a number of clusters. I need a way of determining how many clusters there are, probably by density, and to return a point for the centre of each. 

I've made a heatmap in the display section of the points layer by setting a radius and weighting by the frequency field and in this created three clusters in my trial area, that look right, but I don't see how to get a coordinate for them. Any suggestions of what tool(s) to look at.

Identifying clusters in vector point data using QGIS? is basically the same, but as none of the answers explain how I can do weighted cluster analysis in QGIS. I don't know postGIS or R, and the plugin manageR that was cited no longer seems to exist.