> Thanks. Would you mind pointing me in the direction of any documentation 
> on that particular method, please? 

http://narray.rubyforge.org/SPEC.en
is the only documentation.

> I presume that the (10,10,10,10) 
> refers to the dimensions of the dimensions of the new array (the first 
> three 10s) and the step size to iterate (the last 10)

reshape changes the shape of NArray without changing internal 
arrangement.
In this case, it changes the last dimension with 100 elements into
2-dimensions with 10x10 elements.

> but I am not sure about the mean(3).

in SPEC.en:

Statistics
    self.mean(dim,..)    Mean
    ...
  note: * If dimensions are specified, statistics are performed
          on those dimensions and the rest dimensions are kept.
        * Range can be used.
        * If dimension is not specified, statistics are performed
          for all the elements.
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