The shades of gray represent the relative density of the data points or events.
From the nature.com
It may depend on the relative density of information between different parts of the image and the whole.
From the newscientist.com
For a general use of specific gravity, see relative density.
From the en.wikipedia.org
High grade and ultra high grade anthracite are harder than standard grade anthracite, and have a higher relative density.
From the en.wikipedia.org
Stemplots are useful for displaying the relative density and shape of the data, giving the reader a quick overview of distribution.
From the en.wikipedia.org
Specific gravity, also known as relative density, varies depending upon the chemical composition and crystal structure type.
From the en.wikipedia.org
The technology works by detecting the relative density of protons in water molecules and tracking their movement in response to a magnetic field produced by a nearby coil.
From the newscientist.com
Generally, it is accepted that tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere.
From the en.wikipedia.org
To quantitatively evaluate the sensing characteristics of the FBAR of syndapin 1 we measured the relative density of FBAR on tubes of a range of radii as a function of bulk protein concentration.