Calculate the slope of a single variable.
The slope is calculated using the first
order of a ordinary least squares
The list of values for the single
single variable are processed as Y-values
that are evenly spaced on the X-axis.
This is useful as a simple determination
if the variable is increasing or decreasing.
The slope value is represented as a double
with the key SLOPE in the aggregate result.
If the window to be aggregated contains less than
two values then no regression is performed.
Returns the enum constant of this type with the specified name.
The string must match exactly an identifier used to declare an
enum constant in this type. (Extraneous whitespace characters are
name - the name of the enum constant to be returned.