plotps.m

function h = plotps(lat,lon,varargin)
% plotps works just like Matlab's plot function, but plots georeferenced
% data in Antarctic polar stereographic coordinates (true latitude 71°S).
% 
%  plotps(lat,lon) 
% 
% is equivalent to: 
% 
%  [x,y] = ll2ps(lat,lon); 
%  plot(x,y) 
% 
%% Syntax
% 
%  plotps(lat,lon)
%  plotps(...,LineSpec)
%  plotps(...,'PropertyName',PropertyValue,...)
%  plotps(...,'km')
%  plotps(...,'meridian',meridian)
%  h = plotps(...)
% 
%% Description 
% 
% plotps(lat,lon) plots georeferenced data in Antarctic polar stereographic
% eastings and northings. 
% 
% plotps(...,LineSpec) specifies line or marker style. 
% 
% plotps(...,'PropertyName',PropertyValue,...) specifies any number of
% line or marker properties. 
% 
% plotps(...,'km') plots in polar stereographic kilometers instead of the
% default meters. 
% 
% plotps(...,'meridian',meridian) specifies a meridian longitude in the 
% polar stereographic coordinate conversion. Default meridian is 0. 
% 
% h = plotps(...) returns a column vector of handles to lineseries objects, 
% one handle per line.
% 
%% Examples
% 
% Place a red star at (80°S, 120°W):
% 
% bedmap2('gl','xy')  
% plotps(-80,-120,'rp')
% xlabel('eastings (m)') 
% ylabel('northings (m)')
% 
% Plot a line from the South Pole to McMurdo Station: 
% 
% [mcmlat,mcmlon] = scarloc('mcmurdo station'); 
% plotps([-90 mcmlat],[0 mcmlon])
% 
%% Citing Antarctic Mapping Tools
% This function was developed for Antarctic Mapping Tools for Matlab (AMT). If AMT is useful for you,
% please cite our paper: 
% 
% Greene, C. A., Gwyther, D. E., & Blankenship, D. D. Antarctic Mapping Tools for Matlab. 
% Computers & Geosciences. 104 (2017) pp.151-157. 
% http://dx.doi.org/10.1016/j.cageo.2016.08.003
% 
% @article{amt,
%   title={{Antarctic Mapping Tools for \textsc{Matlab}}},
%   author={Greene, Chad A and Gwyther, David E and Blankenship, Donald D},
%   journal={Computers \& Geosciences},
%   year={2017},
%   volume={104},
%   pages={151--157},
%   publisher={Elsevier}, 
%   doi={10.1016/j.cageo.2016.08.003}, 
%   url={http://www.sciencedirect.com/science/article/pii/S0098300416302163}
% }
%   
%% Author Info
% This function was written by Chad A. Greene of the University of Texas
% Institute for Geophysics (UTIG), February 2015, for inclusion in the
% Antarctic Mapping Tools package. 
% 
% Updated July 2015 to allow plotting in polar stereographic kilometers.
% Updated August 2018 to allow setting the meridian. 
%
% See also: plot, plotm, ll2ps, pcolorps, and patchps. 

%% Input checks: 

assert(nargin>1,'The plotps function requires at least two input: lat and lon.') 
assert(isnumeric(lat)==1,'plotps requires numeric inputs first.') 
assert(isnumeric(lon)==1,'plotps requires numeric inputs first.') 
assert(max(abs(lat(:)))<=90,'I suspect you have entered silly data into plotps because some of your latitudes have absolute values exceeding 90 degrees.') 

%% Parse inputs

plotkm = false; % by default, plot in meters 
meridian = 0;   % top of the map is Fimbul Ice Shelf

% Has user requested plotting in kilometers? 
if nargin > 2
   tmp = strcmpi(varargin,'km'); 
   if any(tmp)
      plotkm = true; 
      varargin = varargin(~tmp); 
   end
   
   tmp = strcmpi(varargin,'meridian'); 
   if any(tmp)
      meridian = varargin{find(tmp)+1}; 
      assert(isscalar(meridian)==1,'Error: meridian must be a scalar longitude.') 
      tmp(find(tmp)+1) = true; 
      varargin = varargin(~tmp); 
   end
end

%% Get initial conditions 

da = daspect; 
da = [1 1 da(3)]; 
hld = ishold; 
hold on

%% Convert units and plot: 

[x,y] = ll2ps(lat,lon,'meridian',meridian); 

% Convert to kilometers if user requested:
if plotkm
    x = x/1000; 
    y = y/1000; 
end

h = plot(x,y,varargin{:}); 
hold on; 

%% Put things back the way we found them: 

daspect(da)

if ~hld
   hold off
end

%% Clean up: 

if nargout==0
    clear h
end

end