## Finding the Rate of Change of a Mapping Output

The astRateastRate function can be used to find the rate of change of any MappingMapping output with respect to any Mapping input, at a given input position. The method used produces good accuracy (typically a relative error of 10E-10 or less) but may require the Mapping to be evaluated 100 or more times. An estimate of the second derivative is also produced by this function.