SIGMA and STANDARD DEVIATION

[Luca1988SCENE]

Hi Daniel, sorry i would to ask what is the difference between SIGMA and STANDARD DEVIATION. i compute a distance between a cloud and its best fit plane by the function "compute cloud/mesh distance" and i see the aprox results(max, min, mean and SIGMA wich is a st. dev). Then i compute the gauss distribuition and there is a new value of st. dev. wich is the most accurate value?
Then , why with the first way CC gives a mean value different to zero and in the second way the mean value ( in guass distribuition) is equal to zero ?Thanks

[daniel]

Well, if you speak of the 'approximate' statistics that are displayed before the distance computation, then as they are really approximate, they don't have necessarily much in common with the true distances (this is why I've hidden them by default now, because too many people were looking at them as if they were accurate!).

The real statistics are output in the Console once the distances are actually computed. And you should get the same values when fitting a Gaussian distribution.

[Aitor]

Hi, I 'm computing "cloud / cloud distances" and I wonder if I can get the results of the mean and standard deviation more accurately than in the Approx results.
You say that the true statistics are issued on the console once the distances are calculated actually but these results are of Gaussian distribution or average true of my scalar values ​​?
Thanks

[daniel]

1st rule: NEVER USE THE APPROXIMATE DISTANCES RESULTS for anything else than settings the octree level and the 'max distance' threshold (if you really need to change them).

Then, I'm not sure what you mean by 'of Gaussian distribution or average true'? The classical definition of the 'average' value IS the average of a Gaussian distribution. The value displayed in the Console at the end of the process is the average distance (i.e. simply the sum of the distances divided by the number of points).

And you can get the exact same quantity by calling the 'Edit > SF > Compute Stat Params' with the Gaussian distribution with the distances SF activated.

Am I missing something?

[Aitor]

it's okay
When I said " average true " i wanted to say " the mean of my values."
I thought the values ​​that appear in the console were the mean and the std deviation of gaussian distribution statistics and not the mean and the std deviation of my values.But are the same!Thanks

[Aitor]

it is not about this topic but....
is it possible to compare the same Scalar fields of diferent point cloud.For Example: Curvature Scalar field of two diferent clouds of diferent years with diferent coordenates. Thanks

[daniel]

Nope :)