In a related post I wrote about one of my favorite visualizations, the Decomposition Tree.  This time I'll write about one I like even more--the Heat Map (or in Microsoft terminology, the Performance Map).

As I said before, state-of-the art BI tools enable a level of exploration and data visualization beyond our wildest imagination when I started in BI 15 years ago. Heat Maps (Performance Maps) are becoming more and more popular in fields from molecular biology to news web sites.  In analyzing performance in a business or non-profit organization, Heat Maps are really fantastic!

Heat maps are especially useful because they show the relationship between two measurements at once, and make it easy to compare a large set of entities to each other to spot patterns and exceptions.  Using a heat map is simple if you know a few simple rules:

1. The heat map has a rectangle for each member of a group being analyzed. For example, if a company has 100 products, the heat map would have 100 rectangles, one for each product.
2. The size of a rectangle expresses the magnitude of the first metric compared to the others.  This metric is typically something like “Sales”, “Cost”, “Profit”, etc.
3. The color of a rectangle expresses the magnitude of the second measurement, with one color implying “positive”, and a second color implying “negative”.  For example, Green=Profit, Red=Loss. This second measurement is often expressed a ratio or percentage.
4. The heat map is organized so that the members with the largest rectangles are at the top-left; the smallest rectangles are at the bottom-right.
5. The brighter the color, the more extreme the measure is.  For example, “Bright Green” = “Really Great!”; “Bright Red” = “Really Poor”. 

With that much introduction, the following heat map should be pretty easy to read.  In this Performance Map, the size of the rectangles are "Sales $", and the color is "Margin %".  At the top left is the biggest-selling product by "Sales $", the PEM1409436.

But it’s margin % isn’t the best or worst, but since it's green (not red), it's good. In the center of the map is the worst Margin %--it’s the bright red rectangle.  Just above that one is the product with the best margin % (bright green).

The beauty of the map is that in 5-10 seconds you just reviewed the performance of almost 100 products, and focused on the problem areas, and their relative priority.  How long it would have taken to do all that in Excel?