Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

the point represents rates like 10%, etc. (this was also pretty clear from 2 years ago) -- been trying to do this for 2 yrs...

the points dont represent numbers of events since they are rates (Finding largest number of observations within a given radius)

but the points have geo ids so they are attached to location, not distance (whatever distance is to imply) -- update: it represents z-value but we're just dealing with rates

share|improve this question
2  
This sounds exactly like gis.stackexchange.com/questions/41956/… (just change "populations" to "rates"). Would that perhaps answer your question? –  whuber Feb 4 '13 at 14:55
    
"populations" are numbers, not rates. "population growths" are rates ^_^" –  kittensatplay Feb 7 '13 at 5:01
add comment

1 Answer

up vote 6 down vote accepted

Yes, the Heatmap plugin can be used for this.

Suppose we have a point layer called pointrates.shp with rates between 0 and 1 associated with each point:

We can run the Heatmap plugin on this, using a Decay Ratio of 1 (which means that the value at the edge of each search radius is the same as at the center), and using the "Ratio" column as the Weight. In this example, I'm using a search radius of 200 km.

This gives us the following map:

As you can see, the values range from 0 to 1.2 (the sum of 0.1, 0.2, 0.4 and 0.5 in the cluster of points in the lower right). Now sums of rates are usually not very meaningful, so a map of averages (rather than sums) is probably more useful. To get this, we'll calculate another Heatmap, this time not using the "Rates" column for the weights. That way, all points will have a weight of 1, and the resulting map is simply a count of points:

The values now range from 0 to 4. To get the average value, we simply use the Raster Calculator to divide the "Sums" map by the "Count" map:

And this gives us our map of averages:

share|improve this answer
    
unable to test -- gis.stackexchange.com/questions/50219/… –  kittensatplay Feb 7 '13 at 5:01
2  
@kittensatplay - why not test with a dummy data? –  vinayan Feb 7 '13 at 5:06
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.