You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: circle_graph_layout.m
    path of file: ./repos/CBIG/external_packages/matlab/default_packages/matlab_bgl
    
    the code of the file until where you have to start completion: function X = circle_graph_layout(G,radius)
% CIRCLE_LAYOUT Layout the vertices of a graph on a circle
% 
% X = circle_layout(G) generates a layout of graph with vertices uniformly
% placed on the circle.  This function does no interesting layout and just
% places the vertices around the circle in order.
%
% X = circle_layout(G,radius) places the vertices with a radius other than
% 1.0.
%
% Example:
%   G = cycle_graph(6);

    
function X = circle_graph_layout(G,radius)
% CIRCLE_LAYOUT Layout the vertices of a graph on a circle
% 
% X = circle_layout(G) generates a layout of graph with vertices uniformly
% placed on the circle.  This function does no interesting layout and just
% places the vertices around the circle in order.
%
% X = circle_layout(G,radius) places the vertices with a radius other than
% 1.0.
%
% Example:
%   G = cycle_graph(6);
%   X = circle_graph_layout(G);
%   gplot(G,X);

% David F. Gleich
% Copyright, Stanford University, 2008

%% History
%  2008-09-25: Initial coding
%%

if ~exist('radius','var') || isempty(radius), radius = 1.0; end