title: Converting Array{Array{Float64,1},1} to Array{Float64,2} in Julia
body: <p>My problem is similar to the problem described <a href="https://stackoverflow.com/questions/29164632/how-to-convert-arrayarrayfloat64-1-1-to-matrix-in-julia?rq=1">earlier</a>,
   with the difference that I don't input numbers manually. Thus the accepted answer there does not work for me.</p>
  
  <p>I want to convert the vector of cartesian coordinates to polars: </p>
  
  <pre><code>function cart2pol(x0,
                    x1)
      rho = sqrt(x0^2 + x1^2)
      phi = atan2(x1, x0)
      return [rho, phi]
  end
  
  @vectorize_2arg Number cart2pol
  
  function cart2pol(x)
      x1 = view(x,:,1)
      x2 = view(x,:,2)
      return cart2pol(x1, x2)
  end
  
  
  
  x = rand(5,2)
  
  vcat(cart2pol(x))
  </code></pre>
  
  <p>The last command does not collect Arrays for some reason, returning the output of type <code>5-element Array{Array{Float64,1},1}</code>. Any idea how to cast it to <code>Array{Float64,2}</code>? </p>