Hi Barend,
Thanks for the observations and grumbles! I was thinking of giving the
observer three choices:
(1) the one I've got now: a ratio of the region's value to the maximum
value on the scale, which in the case of some variables overly condenses
the chromatic range
(2) a measure which calibrates the value map according to a region's value
relative to min = light and max = dark
and
(3) one that merely rank orders the regions by value
The last would maximize visual discrimination of subtleties, while obscuring
quantitative magnitudes. I think (2) is probably what most maps do, so would
that make sense as a default presentation? It is sort of philosophically
between (1) and (3) .
Ultimately, I'd like the observer to be able to choose her own "data spigot"
from any URL on the web that presents a column of state-related data in
easily parseable form, or to meta-mine search data for queries like "alabama
shoes" through "wyoming shoes" from a search engine, to make the shell
infinitely extensible, but am trying to get permission from search providers
for such meta-mining.
I'll have to figure out a way to find the real estate for the title on
screens with "funny" aspect ratios.
A fun thing about this is how little server-side script there is, just ten
lines, and requiring just one linear pass of the dataset per user-chosen
variable -- that should, in theory, make it fast and extensible to very
large datasets. My understanding is that PHP caches a lot of the memory so
that reuse of the same data source may be optimized server-side:
<?php
$f="/mydatafile";
$o=file($f);
$data="";
for ($i=0;$i<count($o);$i++){
$line=explode(",",$o[$i]);
$data=$data.$line[$num].",";
}
echo $data;
?>
best,
David
---------
PS I'll need to learn a bit of an introduction to the cartographer's art and
science, since I suspect I'll be in over my head next semester. Tips like
this are sought!
----- Original Message -----
From: "Barend Köbben" <[email protected]>
To: <[email protected]>
Sent: Tuesday, November 23, 2010 2:47 AM
Subject: Re: [svg-developers] US Map with US Census data
Nice.
<cartographer grumble>
don't use a value map (choropleth) for absolute values (data of
measurement level ratio),
Its perception properties makes for confused readers...
</cartographer grumble>
:-) as an example of the power of SVG (for which I am sure it was meant), it
is of course excellent. Note that on a display with portrait ratio the map
is obscuring the title.
Yours,
--
Barend Köbben (Senior Lecturer)
ITC - University of Twente, Faculty of Geo-Information
Science and Earth Observation
PO Box 217, 7500AE Enschede (The Netherlands)
+31-(0)53 4874 253
From: ddailey <[email protected]<mailto:[email protected]>>
Reply-To:
"[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
Date: Sun, 21 Nov 2010 22:12:52 +0100
To: "[email protected]<mailto:[email protected]>"
<[email protected]<mailto:[email protected]>>
Subject: [svg-developers] US Map with US Census data
Here's a little something I cobbled together in the past couple of days.
http://granite.sru.edu/~ddailey/usmap.svg
It works in Opera, Firefox, Chrome and Safari, but not in ASV(IE). I've not
tested it in IE9, but would be interested to know if it works there.
I took a gnu-licensed SVG map from Wikimedia Commons and then wrote AJAX and
JavaScript and PHP to take data from the US Census bureau's 82 variable set,
shading the states accordingly. After a variable is chosen then you can
mouseover each state to see its numeric value on that variable.
Since it borrows from something with a GNU license I suppose you can't make
profit out of it, but feel free to improve and share!
cheers
David
[Non-text portions of this message have been removed]
Faculty of Geo-Information Science and Earth Observation (ITC)
University of Twente
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