def plot opts={}
          options = {
            type: :scatter
          }.merge(opts)

          x_axis  = options[:type] == :scatter ? Array.new(size) { |i| i } : @index.to_a
          plot    = Nyaplot::Plot.new
          diagram = create_diagram plot, options[:type], x_axis

          yield plot, diagram if block_given?
          plot
        end
Plots a Vector with Nyaplot on IRuby using the given options. Yields the
plot object (Nyaplot::Plot) and the diagram object (Nyaplot::Diagram)
to the block, which can be used for setting various options as per the
Nyaplot API.

== Options
type (:scatter, :bar, :histogram), title, x_label, y_label, color(true/false)

== Usage
vector = Daru::Vector.new [10,20,30,40], [:one, :two, :three, :four]
vector.plot(type: :bar) do |plot|
plot.title "My first plot"
plot.width 1200
end