AVR-Chat

Are there other measures of "spread" of data besides standard deviation
that would be useful?

Jim

>> Mean of N samples is (1/N) sum(Xi) where Xi is one of the samples X0,
>> X1,
>> ... XN-1
>
> Right, I've got that working, but they're telling me that they do NOT
> maintain any history other than their mean and standard deviation
> values!
> I'm also told (last 10 mins) that they are not using the words "mean"
> and "standard deviation" in the classical sense.
>
>> Now if you are doing a total mean rather than a windowed mean (most
>> recent
>> N samples), then the new mean value is
>>
>> Mean = (N*MeanPrevious + Xnew)/(N+1)
>
> Right.
>
>> Not sure that there is a way to do this for standard deviation because
>> if
>> the mean changes, then all the difference values change. That is the
>> hard
>>  part.
>
> That's what's bugging me.. It looks like I could chew up an AVR
> processing a small number of sensors this way, yet they do it with
> multiple megapixel images in realtime. (granted, on quad-core
> machines... but...)
>