Visualisation

Often, presentations and documents make complex points. It’s useful to convey these as a simple visual. It’s worthwhile to make the effort and do a simple visual for every slide or paragraph.

Once, a retail bank asked us if they should centralise their operations. They had operations distributed across branches, regional hubs, and a central hub. After 2 months of work, this was our story:

1. Centralising smoothens demand
2. Centralising improves productivity
3. Your activities are decentralised (so you should consolidate)
4. To do that effectively, you need a few more regional hubs

Centralising smoothens demand

The mathematics is simple. If you have operations in two hubs, A and B, the variance (in demand) for A and B, individually, will exceed the variance for a combined hub A+B. Therefore, you’ll have a smoother demand for the combined hub.

Var(A) + Var(B) >= Var(A+B)

But we couldn’t just say that in a slide. So we collected data about the daily volumes at three hubs, and it clearly showed the result. Var(A) + Var(B) + Var(C) > Var(A+B+C).

But it’s tough to get the message instantly from this. The main problem is, it’s not obvious how variance (a mathematical concept) relates to smoothening demand. So we showed a graph of the load, with individual hubs on the left and the combined hub on the right.

It’s very easy to see this from the graph: demand at the individual hubs varies more than at the combined hub. People would take one look at it and go, “Oh, yeah… I get it. Move on.” (Incidentally, that’s the best possible outcome for a slide. People glance at it, say “Oh yeah, that’s clear. Move on.” It’s what we dream of.)

I have managed to fill hard disks of all capacities within a few months. My first PC had 10MB of disk space, while I work on 140GB today (remember: that’s 14 thousand times more capacity in 14 years). Both were filled within 2 months. (An aside: the number of files / folders hasn’t growth by 14,000. The files themselves have grown in size. I have roughly the same number of files/folders today on my machine as I had 14 years ago.)

To regain space, I used to go through every file and delete the unnecessary ones. My favourite tool was the UNIX utility du (Disk Usage). It lists the disk space used by every subdirectory. I would sort the result and find big, useless stuff. Here are the first few lines of a sorted du output:

1342507	./Books
1188020	./Non-Fiction
1047607	./Comics
842832	./Non-Fiction.Magazines
594939	./Audio
298737	./Books/kokona – Business
172166	./Books/Terry Pratchett
164246	./Books/Terry Pratchett/Discworld
162287	./Calvin
142274	./Books/S
77407	./Scripts
74858	./Science

It would take 5 minutes to create the list, and 15 minutes to read.

Nowadays I use WinDirStat, which shows every file and folder in an intuitive, graphical manner.

This view is called a Treemap. Each small block is a file. Bigger blocks are folders. Colours indicate the type of file (MP3s are blue, AVIs are red, WMVs are yellow, JPGs are green, etc.). This view has many advantages:

• I can see the relative sizes of files and folders.
• I can get an idea of the % of free space (grey block).
• I can see what type of files occupy the most space.
• etc. etc.

But the most important thing is, I see the useful stuff at a single glance.

That’s the key in visualisation: conveying a complex topic so people get it in a second.

(Incidentally, Google has a TechTalk on visualisation, including treemaps.)

Data visualization. Examples of charts that convey a lot of information in a visually obvious way.

The Megapenny Project helps you visualise how big ‘big money’ is, by stacking pennies up. Our highly paid friends at IIM-B would earn a 6′ block of metal each year.