[Qgis-user] Dot Density Symbology

[Shinoto, PD Dr. Maria]

Good to learn about the various options.

The uniform set of polygons is an excellent solution to get a more balanced idea of the density distribution.

The problem is that you need to know whether your point is located inside this polygon or not, and as far as I understand, for that, you need to know the geolocation.

In my case -- and as it seems in the OP's case -- the problem is that we do not know the exact geolocation but know the location in one administrative unit among many of various sizes.

In an example with two units, A with 100sqkm and 200 points, and B with 1000 sqm and 200 points, the shade for density explains the difference, but in my impression, "B" looks like there are more points distributed over a wide area. This is why I like the random distribution of points inside the administrative area; each point may display a specific count of points or, in a next step, a particular density.

I hope I got it right; I am inspired by the ArcGIS example the OP posted.

Maria







Am 2023/07/28 um 02:24 schrieb C Hamilton <adenaculture at gmail.com>:

This may not be an answer to your question, but the Density Analysis plugin (https://plugins.qgis.org/plugins/densityanalysis/) will create a uniform set of polygons over an area of interest with a NUMPOINTS attribute of the number of points are contained within the polygon. The NUMPOINTS value can be weighted using some other attribute. It will automatically style the density map as well from a given color ramp.

Calvin

On Wed, Jul 26, 2023 at 8:06 PM Shinoto, PD Dr. Maria via QGIS-User <qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>> wrote:
Hi,

I have a similar research problem, and the dots seem to be a wonderful solution.

So, this email does not give any assistance re the original question, just an answer to the question below:

Am 2023/07/27 um 03:45 schrieb chris hermansen via QGIS-User <qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>>:

Here's (apologies for the closed source link) an example of the type of map/symbology I'm trying to describe.https://www.arcgis.com/apps/mapviewer/index.html?webmap=30d2e10d4d694b3eb4dc4d2e58dbb5a5

Thanks for any suggestions!

What about just shading the polygons using a gray scale?

Given that your polygons should generate a uniform density of dots within the area they bound, I don't see value in generating the dots for symbology.

The polygon area may vary, as it does in my research (distribution of burials in administrative areas). Therefore, a small area always looks underrepresented as compared to a larger area, and vice versa. I have large administrative areas with low densitiy, but they look well populated even with a very light shade of grey.

So I would like to try to find a solution to Chris' problem since the representation with dots is closer to reality than colouring areas. I will report when I found a solution for my use case -- though this may be autumn...

Maria
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