Posts Tagged ‘johnson’

Noncontiguous Area Cartograms (IndieMaps)

Monday, March 2nd, 2009

[Editor's note: Zach Johnson promotes his Actionscript 3 class for producing non-continuous cartograms and gives background on why these are better (and easier to construct) than Gaster-Newman continuous cartograms.]

Excerpted from IndieMaps blog by Zach Johnson.
View full blog post from Dec. 4, 2008.

Fully contiguous cartograms have stretched and distorted borders but perfectly maintained topologies. Like the Gastner-Newman diffusion-based cartograms we see all over the place. Though all sorts of cartogram designs have been produced, those with perfect topology preservation (fully contiguous cartograms) receive the majority of academic and popular press attention.

< snip >

Judy Olson (Wisconsin Geography alum natch) wrote the only academic article to focus specifically on this cartogram symbology in 1976. She believed noncontiguous cartograms held three potential advantages over contiguous cartograms (I’ve three more below):

  1. “the empty areas, or gaps, between observation units are meaningful representations of discrepancies of values, these discrepancies generally being a major reason for constructing a cartogram”
  2. production of noncontiguous cartograms involves “only the discrete units for which information is available and only the lines which can be accurately relocated on the original map appear on the noncontiguous cartogram”
  3. because of perfect shape preservation, “recognition of the units represented is relatively uncomplicated for the reader”

Despite these inherent advantages (along with ease of production), all the early value-by-area cartograms I’ve seen maintain contiguity. Some took the radical step of abstracting features to geometric primitives, like Levasseur’s early French examples (which may not have been cartograms) and Erwin Raisz’s early American “rectangular statistical cartograms”. But in many ways the noncontiguous design is the more radical cartogram, as it actually breaks the basemap apart — rather than skewing shared borders it abandons them.

my [his] AS3 classes

Olson outlines a technique — the projector method — for manually producing such cartograms. A projector capable of precise numeric reduction/enlargement was required, but not much else, and accurate cartograms could be produced in minutes. A scaling factor was calculated for each enumeration unit, the projector was set to this value, and the projected borders were traced, keeping units centered on their original centers.

My [his] AS3 NoncontiguousCartogram class works similarly. It takes an array of objects containing geometry and attribute properties and creates a noncontiguous cartogram. I include methods for creating the input array from a shapefile/dbf combo, but using KML, WKT, or geoJSON representations wouldn’t be too hard. Methods are included for projecting this lat/long linework (to Lambert’s Conformal Conic projection at least). The NoncontiguousCartogram class draws the input geography, figures the area of each feature, and scales figures according to their density in the chosen thematic variable.

It’s all good/in ActionScript 3, so can be used in Flash or Flex. The zip distribution includes the following:

  • the main class
  • two example applications and the data needed to run them
  • utility classes, including some that make creating cartograms from shp/dbf input quite easy
  • Edwin Van Rijkom’s SHP and DBF libraries, which are used to load the shapefiles in both of the included examples
  • Keith Peters’ MinimalComps AS3 component library, for the components used in one of the examples
  • Grant Skinner’s gTween class, which is required by the NoncontiguousCartogram class for tween transitions

Browse all the above or download the zip.


more advantages

In my thesis research last spring, noncontiguous cartograms performed quite well: subjects rated them highly on aesthetics and could locate and estimate the areas of features with relatively high accuracy. I would add the following to Olson’s list of noncontiguous cartogram advantages.

  1. Olson concentrates on the perfect shape preservation of noncontiguous cartograms. The form (well, those with units centered on the original enumeration unit centroids, as in Olson’s projector method) also perfectly preserves the location of the features on the resultant transformed cartogram. Not only are features easier to recognize, but locations within the transformed units can be accurately located as well (cities or mountain ranges from the original geography can be accurately plotted on the transformed cartogram).
  2. Because units are separate on the transformed cartogram, their figure-ground is increased and areas of features can therefore be more accurately estimated.
  3. Many cartogram designs (including most manual cartograms and the Gastner-Newman-produced cartograms) sacrifice some accuracy for shape recognition. This is a defensible tradeoff, especially as area estimation is notoriously inaccurate and nonlinear. Yet it’s a tradeoff that noncontigous cartograms need not make, as they can always perfectly represent the data with relative areas without sacrificing shape preservation.

Thus, noncontiguous cartograms seem to excel at the cartogram’s two main map-reading tasks: shape recognition and area estimation. This is mediated somewhat by the chief advantage of contiguous cartograms: compactness. Because no space is created between enumeration units, contiguous cartogram enumeration units can be larger than those on noncontiguous cartograms, all other things equal. The increased size on contiguous cartograms may improves their legibility.

Read the full entry over at Indie Maps . . .

Nightingale’s roses in ActionScript 3 (indiemaps)

Tuesday, November 11th, 2008

[Editor's note: Zach Johnson demonstrates how to create animated coxcomb charts in Flash/Flex AS3.]

Republished from

[Zach has] long been a sucker for the polar area/coxcomb/rose charts popularized by Florence Nightingale. These multivariate charts can show ordered or unordered categorical data. As noted in an Economist piece on influential information graphics,

As with today’s pie charts, the area of each wedge is proportional to the figure it stands for, but it is the radius of each slice (the distance from the common centre to the outer edge) rather than the angle that is altered to achieve this.

I wanted to produce some just for kicks, so looked around for a script in AS3. No dice. OK, any language? Didn’t see anything. So I sat on the idea for a while and then finally thought up the technique that made producing them in AS3 quite easy. With the resultant classes, producing graphics like the following small multiples of U.S. soldier deaths in Iraq is a snap. The classes are written in AS3, so can be used with Flash, Flex, or mxmlc. All the example screenshots below are PNGs captured from SWFs produced with only AS3 (extended Sprites). To see the code (which includes a lot of ugly annotation), click ‘view source‘ below any image. All source code is included in the ZIP distribution linked below.


Shaky Economy Challenges Ambitious Obama Agenda (WSJ)

Tuesday, August 26th, 2008


[Editor's note: Glorified timeline with head shots and key issues and economic conditions facing the past three democratic presidents near the beginning of their terms, and the conditions Sen. Obama would face if elected. Republished from the Wall Street Journal. View full size graphic.]

Stocks and Housing Falter as Democrats’ Convention Opens

August 26, 2008; Page A1

Democrats convened in Denver on Monday with the economy’s woes muscling to the top of political concerns, as reflected in further drops in stocks and housing prices.

The Dow Jones Industrial Average tumbled 241.81 points, or 2.1%, to 11386.25, amid continuing worry over the economic and credit problems. Inventories of unsold homes rose to a record, while prices continued to slip, threatening to delay the housing market’s recovery.

Sen. Barack Obama, whom the party will nominate for president this week, addressed one of the key issues, the parlous state of the government-sponsored buyers of mortgages. “I don’t think we can allow Fannie Mae and Freddie Mac to collapse,” he said at a town-hall meeting in Davenport, Iowa, adding that their shareholders “shouldn’t be protected.”

Against this backdrop, Sen. Obama is proposing to use the government to remake economic policies in a way that hasn’t been seen in Washington in decades.

The last two Democratic presidents, Jimmy Carter and Bill Clinton, were hamstrung by rising deficits, feuds with Democrats in Congress and antigovernment sentiment in Washington. Sen. Obama’s advisers argue that he would be largely free from those constraints, easing the way for him to put in place big government programs, tax increases on the wealthy and trade restraints.

An Obama victory would be nearly certain to usher in a larger Democratic majority, which could give his proposals smoother sailing through Congress. If the economy is faltering if and when he takes office — as most economists and policy experts predict it will be — Mr. Obama would push for a stimulus plan with a price tag of $115 billion, his aides say. The plan would include $1,000 rebates for moderate-income and middle-class families, aid to state and local governments and heavy spending on roads, ports and levees and other infrastructure to create jobs.

Sen. Obama, in campaign appearances and discussions with staff, has said that he would start his term in office with three big economic priorities, apart from a possible stimulus plan. One would be a government health-care plan to cover millions without insurance. Another would be a system of tradable pollution permits to reduce emissions and bankroll alternative-energy projects. He’d also push the first increases in income-tax rates since 1993 and in capital-gains taxes since 1986.

In total, his top priorities would cost hundreds of billions of dollars a year, and some of them might require a stiff increase in regulation.

Rice University presidential historian Douglas Brinkley compares Sen. Obama’s approach on economic issues to the last Democrat to occupy the White House before Mr. Carter: Lyndon Johnson. But, he says, “it would be a Great Society with a small ‘g’ and a small ‘s’” because Sen. Obama isn’t planning anything as sweeping as the creation of Medicare, Medicaid and antipoverty agencies.

No matter what he plans, he might confront circumstances that divert him from his agenda, whether foreign threats from Iraq, Iran or Russia or a recession. Any such contingencies could consume his attention and divert many billions of dollars he would rather use otherwise.

Still, many presidents have pushed through their priorities despite major setbacks. President George W. Bush drove through two rounds of tax cuts while pursuing an unanticipated global war on terror. Ronald Reagan won tax cuts and deregulation despite years of Soviet challenges.

Continued at the Wall Street Journal . . .

Land Contracts, Sales Go To Johnson Associates (Kelso via TWP)

Sunday, July 6th, 2008

[Editor's note: This is my third map that refines the mashup template I've been developing for The Washington Post. Data is loaded via XML so the producer doesn't need to edit the HTML. Option to enable the auto-generated legend below the map (the pop-menu above the map is part of the "legend"). MouseOver tooltip behavior tells the user what the markers are called before they click on them to get full details. Option to zoom in on marker click and get satellite map when the info window is called up.

My favorite feature: on close of the information window that resulted from that marker click the map pans / zooms back to it's prior location. No more "where was I" moments so common with mashups! Goes with an investigative piece, read that here.

WEB EDITOR: Juana Summers -- REPORTERS: Cheryl W. Thompson and Mary Pat Flaherty -- The Washington Post. Interactive by Nathaniel V. Kelso -- The Washington Post. First published June 6, 2008.]

Since County Executive Jack B. Johnson took office in December 2002, his administration has agreed at least 11 times to sell public land to people with ties to Johnson, including a former business partner, a current business partner and several campaign contributors. Johnson said he has not been involved in awarding any of the contracts and has ordered a review of county procedures for selling public land. Those who won the deals said they were not given special treatment. The projects are mapped below.

Interactive graphic mirrored below. Original available here.