>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of Wouter van Ooijen
>Sent: 16 September 2004 15:00
>To: 'Microcontroller discussion list - Public.'
>Subject: RE: [OT] cyclic average.
>
>
>> The problem is the discontinuity in the number system being
>> used. Creating a continuous wrap around number system 
>> representing the compass as 0 to 179 180 -179 to -1 makes all 
>> of the averaging problems go away. Conversion of negative 
>> numbers requires a simple add of 360.
>
>So which formula would you use to calculate the average? 
>Simple sum(Xi)/N does not work: take 170 and -170, sum = 0, 
>average would be 0, correct answer is 180.

Actually, 180 is one correct answer, 0 is the other.  Given two arbitrary
points to average between and no other inforamtion, you do not know how the
heading is varying between samples.  One would naturaly assume that it would
be the smaller angle, but there are no guarantees.

Regards

Mike

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