def collect axis=:vector, &block
      dispatch_to_axis_pl axis, :collect, &block
    end
Iterate over a row or vector and return results in a Daru::Vector.
Specify axis with :vector or :row. Default to :vector.

== Description

The #collect iterator works similar to #map, the only difference
being that it returns a Daru::Vector comprising of the results of
each block run. The resultant Vector has the same index as that
of the axis over which collect has iterated. It also accepts the
optional axis argument.

== Arguments

* +axis+ - The axis to iterate over. Can be :vector (or :column)
or :row. Default to :vector.