[gis_info] FW: Looking for advice on making an updating choropleth

[SMITH Cy * DAS]

Hi folks, we have a question about making good choropleth maps.  See below.

cy

[cid:image001.png at 01D5751C.F5818D60]
Cy Smith, GISP
Enterprise Information Services
Data Governance and Transparency|Geospatial Enterprise Office
(503)378-6066, http://gis.oregon.gov
"Ensuring user-friendly, reliable and secure state technology systems that serve Oregonians."


From: VARGAS Antonio R * DCBS <Antonio.R.Vargas at oregon.gov>
Sent: Thursday, December 3, 2020 9:19 AM
To: SMITH Cy * DAS <Cy.SMITH at oregon.gov>; TANNER Joshua * DAS <Joshua.TANNER at oregon.gov>
Cc: JOHNSON Nathan * DCBS <Nathan.Johnson at oregon.gov>
Subject: Looking for advice on making an updating choropleth

Hello,

I was wondering if you or someone on your team could provide some advice or a reference to best practices that might help with a project.

I've been asked to make a choropleth to illustrate dollar amounts going to each Oregon county to illustrate the progress of a program. The issue I'm having is that leadership would like to update the choropleth with new data each week, and I'm not sure how to choose the color scale to accommodate that.

By the end of its lifespan, the dollar amounts will be roughly an order of magnitude higher than at the start. So, when I choose a color scale with enough room at the high end to account for this in the future, basically every county in today's map is assigned the lowest colors on the scale. One idea we had was to use a continuous color scale, though the colors still end up very similar.

On the other hand, if I were to update the color scale each time the data is updated, so that the data fills the whole color range each time, I expect that the colors assigned to each county wouldn't change much over time. I guess the map would look wholly the same each data update, just with the legend assigning different dollar amounts to each color.

Any advice would be much appreciated.

Kind regards,

Antonio

-----

Antonio R. Vargas
Research Analyst
Division of Financial Regulation
Oregon Dept. of Consumer and Business Services
Office: 971.345.1106

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