independentVarRef — References a predefined signal as an input to a function


An independentVarRef more fully describes the input mapping of the function by pointing to a separate breakpoint definition element. An optional extrapolate attribute describes how to extrapolate the output value when the input value exceeds specified values (default is 'neither,' meaning the value of the table is held constant at the nearest defined value). An optional interpolate attribute indicates how to perform the interpolation within the table (supporting discrete, linear, cubic or quadratic splines). There are three different discrete options: 'discrete' means nearest-neighbor, with an exact mid-point value being rounded in the positive direction; 'floor' means the function takes on the value associated with the next (numerically) higher independent breakpoint as soon as original value is exceeded; and 'ceiling' means the function holds the value associated with each breakpoint until the next (numerically) higher breakpoint value is reached by the independent argument. The default interpolation attribute value is 'linear.' Note also that the option min and max attributes serve to limit the numeric range of the independent (function input) variable; these attributes are independent of and serve as additional range contraints with respect to any minValue or maxValue attribute associated with the independent variable itself. This element allows reuse of common breakpoint values for many tables but with possible differences in interpolation or extrapolation for each use.