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: get_fresnel_zone.m
    path of file: ./repos/mpsim/lib/snr/util
    
    the code of the file until where you have to start completion: % Input:
%   receive antenna height, in meters
%   satellite elevation angle, in degrees
%   satellite azimuth, in degrees (positive clockwise from north)
%   wavelength, either a scalar (in meters) or a string ('L1','L2').
%   zone index (optional); 1 means first Fresnel zone, 0.5 first Fresnel subzone
%   surfa
    
function plotit (answer, f, cmap, prc)
%!   if (nargin < 3) || isempty(cmap),  cmap = 'hsv';  end
%!   if (nargin < 4) || isempty(prc),  prc = 100;  end
%!   img = f(answer.map);
%!   figure
%!   imagesc(answer.info.x_domain, answer.info.y_domain, img)
%!   set(gca, 'YDir','normal')
%!   colorbar
%!   axis image
%!   title(func2str(f), 'Interpreter','none')
%!   grid on
%!   xlabel('East (m)')
%!   ylabel('North (m)')
%!   set(gca, 'XTick',linspace(answer.info.x_domain(1),answer.info.x_domain(end