Junk Charts

Life-enabling charts

In response to my call for positive examples, reader Merle H. sent in an example of how good charts can make our lives simpler and easier.

All of us have seen the following presentation of air travel data.

Not trying to pick on Travelocity - it's the same format whether you use Expedia or any of the airline sites.  For those customers who are looking to decide what dates to travel so as to minimize their air fare, this format is very cumbersome to use.

What about this fare chart at FuncTravel.com?

As you mouse along the line chart, the average fare for each day is visible.  Clicking on a particular day will fix the departure or return dates.

So much easier, isn't it?

A few caveats, though:

• Instead of just providing the historical averages, they should consider including information on variability, such as bars that indicate the middle 50% or 75% of prices.  Also, what about a sliding control for customers to decide which period of past history the averages should use?  More recent data may be more representative.
• This particular feature appeals to the price-sensitive, date-flexible customer segment.  Not everyone will pick itineraries based on those criteria.  There is an easy fix. If some controls are available for customers to indicate other preferences, e.g. exclude all British Airways flights, include only evening flights, etc., and the chart can update itself based on such selections, then the chart becomes a lot more flexible, and useful to many more customers.
• As with many automatically generated charts, the chosen labels on the vertical axis are laughable.  That should be relatively easy to fix, you'd think.
  

A great start.  I happen to notice that Travelocity has a beta feature that shows a similar chart.  A revolution in how travel sites present data to us is long overdue. 

Seth's Rules

(Via Gelman blog)

Prominent marketer Seth Godin came up with some sensible rules for making "graphs that work".  We pretty much agree with most of what he says here, unlike the last time he talked about charting.

One must recognize that he has a very specific type of chart in mind, the purpose of which is to facilitate business decisions.  And not surprisingly, he advocates simple, predictable story-telling.

His first rule: dispense with Excel and Powerpoint.  Agreed but to our dismay, there are not many alternatives out there that sit on corporate computers.  So we need a corollary: assume that Excel will unerringly pick the wrong option, whether it is the gridlines, axis labels, font sizes, colors, etc.  Spend the time to edit every single aspect of the chart!

His second rule: never show a chart for exploration or one that says nothing.  I used to call these charts that murmur but do not opine.  (See here, for example.)  This pretty much condemns the entire class of infographics as graphs that don't work.   This statement will surely drive some mad.  One of the challenges that face infographics is to bridge the gap between exploration and enlightenment, between research and insight.  As I said repeatedly, I value the immense amount of effort taken to impose structure and clarity on massive volumes of data -- but more is needed for these to jump out of the research lab.

In rules 3 and 4, Seth apparently makes a distinction between rules made to be followed and rules made to be broken.  In his view, time going left to right belongs to the former while not using circles belongs to the latter.  He gave a good example of why pictures of white teeth are preferred to pie charts, bravo.  I hope all those marketers are listening.

As readers know, I cannot agree with "don't connect unrelated events".  He's talking about using line charts only for continuous data.  This rule condemns the whole class of profile plots, including interaction charts in which statisticians routinely connect average values across discrete groupings.  The same rule has created the menace of grouped bar charts used almost exclusively to illustrate market research results (dozens to hundreds of pages of these for each study).  I'd file this under rules made to be broken!

What menace?

What menace?

What menace?

What menace?

Alright, I made my point.  If you don't work in market research, the mother lode of cross-tabs and grouped bars, consider yourself lucky.  If you do, will you start making line charts please?

R power, math stats power

Amusingly, the New York Times finally got wind of the R software.   See the article here.

We in the statistics community owe these folks a lot of gratitude for developing such a flexible, powerful software.  It is unfortunate that they didn't mention graphing as one of the great strengths of the software.

Equally amusingly, the Wall Street Journal told us what we already know, that we have the best jobs in the world.  Their discovery here.


 

Lost in translation

Since English is my second language, I have always been intrigued by automatic translation.  My "Turing" test for translation engines is to feed the translated output back into the same engine in the opposite direction.

Case in point: the first sentence of this post is translated by Babelfish into Italian -

Poiché l'inglese è la mia seconda lingua, sono stato incuriosito sempre tramite la traduzione automatica.

Now, Babelfish translates the above Italian text into English, as:

Since English is my second language, has been made curious always through the automatic translation.

Not that bad, really.

The tag line of this blog is "recycling chartjunk into junk art".  What happens in the other direction?  The answer is on this page!

This entry is inspired by Michael M.

Tricks of the trade 2

In a previous post, I explained the value of sketching when creating graphs. Today, I will share a few other graphs that plot the same data as we discussed the other day, regarding the proportion of time spent on developing different modules of software.

A stacked column chart, suggested by John J., would look like this:

Compared to the profile chart, this chart has some weaknesses:

• it's difficult to read off the proportions for middle blocks like Blinksale-Billing;
• because the middle blocks "float", it is impossible to compare them properly;
• it requires as many colors as there are variables.

These problems get worse as the data scale: more difficult to read off the data; more colors needed.

The Merrimecko, suggested by Bernard L., is the same chart as above except that the widths of the columns are made proportional to the relative number of lines of code.  However, because these four companies do not make up the entire universe, proportional width make little sense here.

The profile chart can be drawn up in two ways:

These charts typically display results of cluster analysis.  This is a statistical data mining technique which discovers groups of like objects within a large data set.  Often times, the computer will only tell you these 15 belong to Cluster 1, those 22 form Cluster 2, etc. 

To figure out why the 15 belong together, the analyst needs to plot the explanatory variables against cluster index.  Now, think of WuFoo, FeedBurner, etc. as clusters, and the proportion of code given to Application, etc. as variables.

While the line segments don't signify anything real, they trace out  the precise paths our eyes would take when reading the stacked column chart above!  Remember we wanted to compare the number of lines given to each function across companies.  If shown the column chart, my eyes would flip across the top of the  Application (blue) blocks from WuFoo to regonline.  This path is exactly the brown line on our first profile chart.

The numbers for Marketing, Support and Billing are much easier to read too as they all start from zero for each company.

The right chart is another possibility but for this particular situation, I prefer the left one.

Finally, I am less familiar with the "parallel coordinates plot" that Derek talked about.  I believe it is a variant of the profile chart.