Function Reference: D
    d	Difference (time-series) functions for series.
 
    @date	Date number of observation.
 
    @dateadd	Date number after applying offset.
 
    @datediff	Difference between two date numbers.
 
    @dateceil	Last possible date in a time period.
 
    @datefloor	Earliest possible date in a time period.
 
    @datenext	First possible date in the next time period.
 
    @datestr	String representation of a date number.
 
    @dateval	Date number associated with a string representation of a date.
 
    @daycount	Number of days of week in observation.
 
    @dbeta	Beta distribution probability density.
 
    @dbinom	Binomial probability function.
 
    @dbname	String containing the default database name .
 
    @dbvnorm	Bivariate normal probability density function.
 
    @dchisq	Chi-square probability density function.
 
    @dcumdn	Difference of cumulative sum of negative (below threshold) changes in a series.
 
    @dcumdp	Difference of cumulative sum of positive (above threshold) changes in a series.
 
    @dcumdz	Difference of cumulative sum of zero (at threshold) changes in a series.
 
    @demean	Compute deviations from the mean of the series.
 
    @demeanby	Compute deviations from the mean of the series by group.
 
    @det	Determinant of matrix.
 
    @detrend	Compute deviations from the trend of the series.
 
    @dexp	Exponential probability density function.
 
    @dextreme	Extreme value (Type I-minimum) distribution function.
 
    @dfdist	F-distribution probability density function.
 
    @dgamma	Gamma probability density function.
 
    @dged	Generalized error probability density function.
 
    @digamma	First derivative of the natural log gamma function.
 
    @diwish	Inverse Wishart probability density function.
 
    @dlaplace	Laplace probability density function.
 
    dlog	Difference functions for natural logarithm of a series.
 
    @dlognorm	Log normal probability density function.
 
    @dmvnorm	Multivariate normal probability density function.
 
    @dnegbin	Negative binomial probability function.
 
    @dnorm	Standard normal probability density function.
 
    @dpareto	Pareto probability density function.
 
    @dtdist	Student’s
 
 probability density function.
 
    @dtoo	Observation number in the workfile associated with a date string.
 
    @dunif	Uniform probability density function.
 
    @dupselem	Identifier for the observation within the set of duplicates.
 
    @dupsid	Identifier for the duplicates group for the observation.
 
    @dupsobs	Number of observations in the corresponding duplicates group.
 
    @during	Indicator of whether an observation is between two dates
 
    @dweib	Weibull probability density function.
 
    @dwish	Wishart probably density function.