Cumulative process of zero (at threshold) changes.
Compute the partial sum process of positive (at the threshold y) changes in the series x beginning in the specified date.
Syntax: @cumdz(x, d[, y, s])
x: series
d: string
y: (optional) number
s: (optional) sample string or object
Return: series
Consider the partial sum decomposition of a variable
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given a initial value
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as
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where
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,
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, and
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are the partial sum processes of the differences for positive, negative, and zero
changes in
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relative to the threshold
y:
This function returns the zero change
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for the current or specified sample.
• The date
d string specification determines
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.
• Values for dates prior to d will be NAs.
• The optional
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argument specifies the threshold value. By default
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.
This function is panel aware.
Examples
show @cumdz(x, 2001, 1)
produces a linked series of @cumdz applied to x where the starting date is 2001 and the threshold value is set to 1.
Cross-references