This is an intriguing problem. To maintain a fixed size buffer containing
a set of n equally spaced in time values that best represent the events
over a time period that is continually increasing.

To ensure there are always n values present (the device could be asked to
dump its contents at any time) and that they faithfully represent the
input time series means the n values must be "adjusted" as each new sample
arrives. The adjustment would have less and less effect as it moves back
in time through the buffer. It also means the sample period must slowly
increase to match the elapsed time period, or else the samples are
accumulated for an increasing time and then a mean taken before being
added to the buffer. While sample period adjustment and the mechanism of
the buffer update is not hard, choosing the "adjustment" algorithm for
each value is.  I am exploring some interpolation and averaging methods
but comparing the buffer contents to an actual n samples of the total time
series at the end of the simulation has significant errors. Anyone else
got any ideas?

Ron

On Mon, 3 Nov 1997, TRESADERN J.M wrote:

> Hi
>
> I am working on a final year project for my degree,
> using a PIC controller as a data logger.  At the
> moment a predefined amount of data is logged for any
> given session time.  What I want to do it allow the
> system to be run for any length of time and still have
> the same amount of data logged (e.g 60 points).
>
> Does anybody have an algorithm or know where to find
> one, that dynamically junks data as the time goes on,
> such that I have a set of data with fairly equal spaces
> in time between them.
> ---------------------------------------
> TRESADERN J.M
> tc801404@stmail.staffs.ac.uk
>

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Ron Kreymborg                   Systems Administrator
 Monash University               CRC for Southern Hemisphere Meteorology
 Wellington Road
 Clayton, VIC 3168               Phone     : 061-3-9905-9671
 Australia                       Fax       : 061-3-9905-9689
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