The XYZ Dataset
An XYZ Dataset is currently only used for bubble charts. This dataset plots on a chart with two numeric axes. The way this dataset is currently implemented, each series has three numeric values - the first two are the X and Y values which denote a point on the chart plot area. The third value, the Z value, determines the size of the circle that is drawn around the XY point.
As you can see, this limits the bubble chart to one point per series. This implementation is very limited in what you can do with a bubble chart. we intend to expand the data processing of the bubble chart in the near future.
There is an open issue (as of Sept. 2007) on bubble charts where if you pass multiple rows with the same series name to a bubble chart, only the last row for that series is rendered. This is due to the limiting code in the data loader portion of this chart implementation.
Column and row based datasets look the same for an XYZ dataset. Each row is expected to have four columns. Each row is assumed to represent one data point on the chart, ordered by the series name and domain value. The first column's values contain the name of the series. The second column is numeric, containing the domain value of the data point. The third column is numeric, containing the range value of the data point. The fourth column is numeric, representing the value to use in the algorithm that determines the size of the bubble drawn around the data point.
A Dataset Example
Here is a query and dataset from the Pentaho sample data that demonstrates an XYZ dataset:
select department, sum(actual) as actual, sum(budget) as budget, sum(variance) as variance from QUADRANT_ACTUALS WHERE NOT department like 'Prof%' group by department
This query results in the following dataset:
Marketing & Communication
Handing this dataset to a chart, the chart will plot the data by column by default. Here is an example: