Working with XYZ Scatter Graphs

First we have to examine the structure of the data and choose an appropriate form of representation.

The data source contains entries for 10 countries, where the following values are provided per country:

1. Actual CO2 emissions for the year 2005, measured in Million Metric Tons of CO2 Equivalent (MMTCO2). They are split into three categories by economy sectors that are major sources of energy-related CO2:

• Electric Power Production
• Transportation
• Industrial, Commercial and Residential

2. Proposed emissions caps for the period 2008-2012 (MMTCO2 per year).

3. Granted emissions caps by the European commission for the same period (MMTCO2 per year).

The values in the first three columns add up to the total emissions for the year 2005, so they can be naturally represented as a stack. The fourth and the fifth values can be placed next to the stack, so that the proposed and granted emissions caps can be easily compared to the actual emissions. The cluster-stack combination that is formed can be displayed as a 2D plot (Fig. 2):

An interesting idea is to make the chart 3-Dimensional and place the bars on top of the Europe map. For this purpose we'll create a Mesh surface series and texture it with a pre-rendered image of the Europe map (Fig. 3). We'll also set the ratio of the X:Z chart dimensions to be equal to the X:Y ratio of the map image, so that the map is not distorted. For example if the image size is 540 x 650 pixels, we set the chart width to 54 and the chart depth to 65.

The XYZ cluster bar chart is a unique feature of Nevron Chart for .NET. It gives us the ability to place each cluster at arbitrary positions along the X and Z axes. We just have to fill the X and Z values in the first bar series of the cluster and set the UseXValues and UseZValues properties of the series to true.

The Y axis shouldn't be very long because otherwise the bars will get taller and will obstruct greater part of the image. With shorter bars the readability is decreased a little bit compared to the 2D chart, but in return we have a chart that looks really impressive (Fig. 4).

Only a few finishing touches remain before the chart is complete. We'll place a title above the chart and a legend that explains the color coding of the bars. The built-in xml formatted texts will come helpful for splitting the long title into two lines and displaying the subscript in "CO2". A soft blurred shadow behind the title gives depth to the final image (Fig. 5).