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I am not arguing with the word "collect", as it can be interpreted in best faith. I DO argue against the "collect near the unit d-sphere", if it does not come
by DoctorOetker 8y ago
I am not arguing with the word "collect", as it can be interpreted in best faith.
I DO argue against the "collect near the unit d-sphere", if it does not come with an explicit pointer or reference to the explanation of this illusion, I don't care if one points to Maxwell Boltzmann speeds vs velocity vector distribution, or Jacobian determinant, but one should point to something else communication makes no sense. We communicate to teacch and learn. Only when explaining why there appears to be a sphere in the higher dimension, and how this illusion arises is communicating about this pseudosphere justified. The unit d-sphere makes no sense on the 1-dimensional axis of absolute length on which we project the samples. A reference to a "unit d-sphere" only makes sense as residing in the original d-dimensional sample space. But in that space there is absolutely no packing of samples near the peak radius as it appears in the distribution of lengths.
I was not responding to the "curse of dimensionality". I show that this effect already exists at low dimensions, and physicists are very acquainted with it because within their first years of university study they get drilled in 1) jacobians for non-linear coordinate transformations 2) the velocity distribution of molecules in the kinetic theory of gases, where there is a similar plot for the absolute speed (Maxwell-Boltzmann) distribution [0] showing a peak at a non-zero speed, even though the velocity vector distribution is a normal distribution... Every physicist worth his / her salt, immediately recognizes the phenomenon as relating to the Jacobian determinant, that this has nothing to do with velocities aggregating to some sphere of non-zero radius, and that this is a misinterpretation of magnitude distribution plot...
Clearly in this physics example d=3. Would you say d=3 already shows the curse of dimensionality? I call bullocks, and suspect a misinterpretation of the magnitude plot...
Again the peak in the magnitude plot is very real, any reference to a sphere with radius of the peak in the magnitude plot and residing in the original d-dimensional space is purely imaginary!
Of course the person with simultaneously avera height, avg weight, avg income, avg capital, avg age, avg ... is very rare, ... but less rare than a similarily accurately specified person with non-average weight, but all other variables still average...
[0] https://en.wikipedia.org/wiki/Maxwell-Boltzmann_distribution#Derivation_and_related_distributions https://en.wikipedia.org/wiki/Maxwell-Boltzmann_distribution...
see the last 2 sections on velocity vector distribution, and speed distribution...