54 lines
1.5 KiB
Plaintext
54 lines
1.5 KiB
Plaintext
|
|
{{alias}}( W )
|
|
Returns an accumulator function which incrementally computes a moving
|
|
product.
|
|
|
|
The `W` parameter defines the number of values over which to compute the
|
|
moving product.
|
|
|
|
If provided a value, the accumulator function returns an updated moving
|
|
product. If not provided a value, the accumulator function returns the
|
|
current moving product.
|
|
|
|
As `W` values are needed to fill the window buffer, the first `W-1` returned
|
|
values are calculated from smaller sample sizes. Until the window is full,
|
|
each returned value is calculated from all provided values.
|
|
|
|
For accumulations over large windows or accumulations of large numbers, care
|
|
should be taken to prevent overflow. Note, however, that overflow/underflow
|
|
may be transient, as the accumulator does not use a double-precision
|
|
floating-point number to store an accumulated product. Instead, the
|
|
accumulator splits an accumulated product into a normalized fraction and
|
|
exponent and updates each component separately. Doing so guards against a
|
|
loss in precision.
|
|
|
|
Parameters
|
|
----------
|
|
W: integer
|
|
Window size.
|
|
|
|
Returns
|
|
-------
|
|
acc: Function
|
|
Accumulator function.
|
|
|
|
Examples
|
|
--------
|
|
> var accumulator = {{alias}}( 3 );
|
|
> var p = accumulator()
|
|
null
|
|
> p = accumulator( 2.0 )
|
|
2.0
|
|
> p = accumulator( -5.0 )
|
|
-10.0
|
|
> p = accumulator( 3.0 )
|
|
-30.0
|
|
> p = accumulator( 5.0 )
|
|
-75.0
|
|
> p = accumulator()
|
|
-75.0
|
|
|
|
See Also
|
|
--------
|
|
|