[GRASS-user] How would I make this odd choropleth in GRASS?

GRASS GRASS user
1

I have a shapefile of US counties in Texas. A map that I am trying to conceive would 1) separate the polygons to add some distance / whitespace between the constituting polygons 2) preserve their relative positioning 3) color the polygons on a graduation of average income and 4) while preserving shapes, increase or decrease size based on population .

Am I crazy, is there such a map ? What would it be called or described as? How could I make this in GRASS?

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2

Hmmm… I would start experimenting by

A) calculate the geographic center of each polygon then around that point reduce size by some 25 percent. This could great gaps between your polygons.

B) when you are happy with A above, then reduce the sizes of the smaller polygons as a proportion of the one with the highest population.

HTH,

Zoltan

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On 19 Jan 2021, at 07:34, Dheeraj Chand <dheeraj@dheerajchand.com> wrote:

I have a shapefile of US counties in Texas. A map that I am trying to conceive would 1) separate the polygons to add some distance / whitespace between the constituting polygons 2) preserve their relative positioning 3) color the polygons on a graduation of average income and 4) while preserving shapes, increase or decrease size based on population . 

Am I crazy, is there such a map ? What would it be called or described as? How could I make this in GRASS?

Sent from my iPhone

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3

Hi,

Am 19. Januar 2021 06:28:37 MEZ schrieb Dheeraj Chand <dheeraj@dheerajchand.com>:

I have a shapefile of US counties in Texas. A map that I am trying to conceive would 1) separate the polygons to add some distance / whitespace between the constituting polygons 2) preserve their relative positioning 3) color the polygons on a graduation of average income and 4) while preserving shapes, increase or decrease size based on population .

Am I crazy, is there such a map ? What would it be called or described as?

This generally called a cartogram or a chorogram: https://en.wikipedia.org/wiki/Cartogram?wprov=sfla1

Today the most used method, AFAIK, is this one:
https://www.pnas.org/content/101/20/7499

How could I make this in GRASS?

You can't make this in GRASS GIS.

You can find code from one of the authors of above paper here: http://www-personal.umich.edu/~mejn/cart/.

QGIS used to have plugin for this: https://plugins.qgis.org/plugins/cartogram/
Don't know if that is still active.

Then there is scapetoad:
http://chorogram.choros.ch/scapetoad/chorogram.php

In R you can use Rcartogram: https://cran.r-project.org/web/packages/cartogram/index.html

Geoda and others also offer this functionality.

Moritz