Comments on: Texas Grows 70% Each Year

By: anonymous

anonymous — Mon, 13 Aug 2012 06:02:22 +0000

One solution might be to use a notation like:

[0-5[ ; [5-10[

It has the advantage of being easily understood, yet it looks pretty ugly in a map legend.

By: Curtis

Curtis — Fri, 21 Jan 2011 05:13:22 +0000

David was exactly right. I began my comment on the intention of stating what he already did. If the “in thousands” was removed the chart is easily read.

Their is one other thing. <5% and <0% are data sets that overlap. But this is not really a big deal. most people will interpret this properly as red being below 0% and the lightest blue color being 0%-5%.

The simplicity of the chart and ease of reading, vastly outweigh the need for perfect nomenclature of the data sets. Stuff like that only bugs obsessive compulsive people. OC's are impossible to please anyhow.

By: Daniel Huffman

Daniel Huffman — Mon, 03 Jan 2011 18:10:22 +0000

Thanks for the kind words, David. You are quite right in that it’s unlikely that a state is on the edge, and I think I have been looking at this problem too much from the side of the data rather than the reader, trying to figure out which number should go into which class, rather than reading each class as a range.

Your comment reminds me of another solution which I forgot to mention. I encourage my students to put the actual class ranges on their legends, rather than trying to give a continuous sequence of numbers. That is, something like: 1-4, 8-9, 11-13, etc. This makes sure there are clear gaps between each class, and gives extra information: there are no states between 4 and 8, for example, and any state in the second class is between 8 and 9 (rather than between 5 and 10, if we were trying to make all the classes adjoin each other numerically). It adds a bit of extra precision to things.

By: David Medeiros

David Medeiros — Mon, 03 Jan 2011 18:00:57 +0000

I think your visual solution is very nice. It might be improved with font and arrow symbol changes but it eliminates the implication of precision that comes with decimal numbers in a legend as well as the value gaps.

For this map I think it can be assumed that no states growth was exactly on the center line of any range so there is probably no ambiguity in determining what color to give each state for the cartographer.For the map reader (ignoring the typo) you can read each range as saying this color represents growth ‘between 5 and 10 percent’ or ‘between 10 and 15 percent’. It’s a range of 5 percent that only returns information that says ‘this states growth was somewhere between 5 and 10 percent’. No confusion or ambiguity actually arises from having repeated values in the ranges since each range statement is likely always correct in this case and delivers the generally the same level of detail as it would if the legend read in more precise decimal values. If a state happens to be directly on the overlap value this argument falls down of course, but I think that’s unlikely.

By: Daniel Huffman

Daniel Huffman — Wed, 22 Dec 2010 22:23:27 +0000

Interval notation might be nice. One of the things I was thinking about here is that we run into problems with using something unfamiliar. But, if we just bit down and started using something that works well and is unfamiliar, eventually we’d create a level of literacy among the map reading populace where this would become familiar.

By: Andy Woodruff

Andy Woodruff — Wed, 22 Dec 2010 19:06:50 +0000

That legend labeling problem is frustrating as a cartographer. Decimals and gaps can be messy in an otherwise orderly legend. (And you have to be sure none of the data actually falls in the gaps—can't write a nice number like 14.9 if one state is actually 14.95.) But clearly showing the ranges can require a legend design that doesn't easily fit within the constraints of the project. Somebody really needs to invent an "up to but not including" symbol that we can use in place of a dash. Perhaps we should stick to interval notation. [5,10), [10,15), and so forth.