function [h]=m_pcolor(long,lat,data,varargin);
%  M_PCOLOR Makes a pcolor image on a map.
%    M_PCOLOR(LONG,LAT,DATA,...) is a pseudocolor  plot of matrix DATA.
%    The values of the elements of DATA specify the color in each
%    cell of the plot. In the default shading mode, 'faceted',
%    each cell has a constant color and the last row and column of
%    DATA are not used. With shading('interp'), each cell has color
%    resulting from bilinear interpolation of the color at its 
%    four vertices and all elements of DATA are used. 
%    The smallest and largest elements of DATA are assigned the first and
%    last colors given in the color table; colors for the remainder of the 
%    elements in DATA are determined by table-lookup within the remainder of 
%    the color table.
%
%    See also M_CONTOUR, CONTOURF, PCOLOR

% Rich Pawlowicz (rich@ocgy.ubc.ca) 17/Jan/1998
%
% This software is provided "as is" without warranty of any kind. But
% it's mine, so you can't sell it.

% 19/02/98 - type - should have been 'clip','patch', rather than 'off'.
%  9/12/98 - handle all-NaN plots without letting contour crash.
% 6/Nov/00 - eliminate returned stuff if ';' neglected (thx to D Byrne)


global MAP_PROJECTION 

% Have to have initialized a map first

if isempty(MAP_PROJECTION),
  disp('No Map Projection initialized - call M_PROJ first!');
  return;
end;

if min(size(long))==1 & min(size(lat))==1,
 [long,lat]=meshgrid(long,lat);
end;

[X,Y]=m_ll2xy(long,lat,'clip','on');  %First find the points outside

i=isnan(X);      % For these we set the *data* to NaN...
data(i)=NaN;

                 % And then recompute positions without clipping. THis
                 % is necessary otherwise contouring fails (X/Y with NaN
                 % is a no-no. Note that this only clips properly down
                 % columns of long/lat - not across rows. In general this
                 % means patches may nto line up properly a right/left edges.
if any(i(:)), [X,Y]=m_ll2xy(long,lat,'clip','patch'); end;  

if any(~i(:)),
 [h]=pcolor(X,Y,data,varargin{:});
 set(h,'tag','m_pcolor');
else
  h=[];
end;

if nargout==0,
 clear  h
end;