I see a lot of references to hierarchical data but what exactly counts as hierarchical data isn't always clear and I can't find a clear definition of what counts as hierarchical data.
For example, the following blog states:
"[neural network are]...particularly suited to complex, hierarchical data"
A few examples are give involving images, etc, but can hierarchical data also include data who's independent variable is continuous?
How would you define hierarchical data, would you be able to provide an example?