Formula of "mean dist" and "standard deviation"

[MarkusM]

Hi there,

I could not figure out how the computation of "mean distance" and "standard deviation" for Cloud/Cloud or Cloud/Mesh Distances work.

Is it something like:

mean dist = sum ( distances ) / n
std deviation = sqrt ( sum ( Xi - Xm )) / n

n: number of all distances
Xi: distance from Point i to its next neighbour
Xm: mean distance

It would be nice if anybody could help me out.

Thanks and Greets
MarkusM

[daniel]

The mean distance is what you suggested:

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mean dist = sum ( distances ) / n

But you forgot a "square" power in the std. deviation equation, and the division is done before the square root:

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std deviation = sqrt ( sum ( Xi - Xm )^2  / n )

Which simplifies in:

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std deviation = sqrt( sum ( Xi )^2 / n - mean^2 ) 

(well at least it's faster to compute ;)

[MarkusM]

Thank you for the quick response!