def add_plots(*plots)
      plots.unshift(0) unless plots[0].is_a?(Numeric)
      self.class.new(@plots.insert(*plots), @options)
    end
def add_plots(*plots)
      plots.unshift(0) unless plots[0].is_a?(Numeric)
      self.class.new(@plots.insert(*plots), @options)
    end
Create new Multiplot with given *plots* added before plot at given *position*.
 (by default it adds plot at the front).

 @param position [Integer] position of plot which you need to replace
   (by default first plot is replace)
 @param plots [Sequence of Plot or Splot] plots you want to add
 @return [Multiplot] self
 @example
   mp = Multiplot.new(Plot.new('sin(x)'), Plot.new('cos(x)'), layout: [2,1])
   enlarged_mp = mp.add_plots(Plot.new('exp(x)')).layout([3,1])
   # mp IS NOT affected