2.1.955 Section 15.35.1, Regression Type

a.   The standard defines chart:regression-type, contained within [style-chart-properties-attlist]

This is supported in core Excel 2007 Excel 2007 uses this attribute for the <style-chart-properties-attlist> element of the <chart:series> element when the series type is "line", "area", "scatter", "bar", "stock", or "bubble", and the chart is not three dimensional.