%VECPLOT routine to plot vectors.  
% VECPLOT draws vectors on the current figure, at (x,y)
% locations determined in one of two ways.  If the first
% argument to VECPLOT is a fem_grid_struct, then VECPLOT
% extracts the FEM domain coordinates as the vector origins.
% Otherwise, the user supplies the (x,y) coordinates
% explicitly.  This flexibility exists because vector
% plotting does not require any knowledge of nodal 
% connectivity, and perhaps the (u,v) data are not
% from a FEM model output.
%
% VECPLOT scales the magnitude of 
% (u,v) by the magnitude of max(abs(u,v)) and then 
% forces a vector of magnitude sc to be 10% of the x data
% range.  By default, sc = 1., so that a 1 m/s vector will
% be scaled to 10% of the x data range.  If sc=.5, then
% a vector magnitude of 50 cm/s  will be scaled to 10% of the 
% x data range.  Decreasing sc serves to make the vectors
% appear larger.  VECPLOT then prompts the user to place
% the vector scale on the figure, unless scale_xor,scale_yor
% is specified (see below).
%      
%   INPUT:   x,y    - vector origins
%            u,v    - vector amplitudes
%            These inputs are optional, but if one is needed, all
%            preceeding it wil be required.
%            sc     - vector scaler; (optional; default = 1.)
%            sclab  - label for vector scale; (optional; default = 'cm/s')
%            scale_xor,scale_yor  -  location to place vector scale
%
%  OUTPUT:   h - vector of handles to the vector lines drawn, the 
%                scale vector, and the scale vector text.
%
%   NOTES:   VECPLOT requires atleast 2 coordinates and vectors.
%
%    CALL:   hv=vecplot(x,y,u,v,sc,sclab)
%
% Calls: none
%
% Written by : Brian O. Blanton
%
function  retval=vecplot(x,y,u,v,sc,sclab,scx,scy)

% Copy incoming cell array

% DEFINE ERROR STRINGS
err1=['Invalid number of input arguments to VECPLOT'];
err2=['Struct to VECPLOT not a valid FEM_GRID_STRUCT.'];
err3=['Length of u,v must be the same'];
err4=['Length of (x,y) must equal length of (u,v).'];
err5=['Alteast 3 arguments are required if first is a fem_grid_struct.'];
err6=['Alteast 4 arguments are required if first two are x,y.'];
err7=['Second optional argument (sclab) must be a string.'];
err8=['Both x- and y-coords of vector scale must be specified.'];


% PROCESS THE INPUT ARGUMENTS
% Length of varargin must be between 3 and 8, inclusive.
if nargin<3 |  nargin>8
   error(err1)
end 

   % If we're here, the first argument to VECPLOT is NOT
   % a structure;  the first 4 arguments are then required 
   % and are x,y,u,v; there is no way to ensure that the
   % order is correct.  Hopefully, said user read the help text!
   if nargin<4
      error(err6)
   end
   xin=x;yin=y;
   uin=u;vin=v;
   % delete the cells accounted for so far;  the remaining will be 
   % processed below;.

% At this point, the copy of the input cell has been reduced to
% contain the optional arguments, if any.
if nargin==4
   sc=1.;sclab=' cm/s';
elseif nargin==5
   sc=sc;
   sclab=' cm/s';
elseif nargin==6
   sc=sc;
   % Make sure second optional arg is char
   if ~isstr(sc)
      error(err7)
   end
   sclab=[' ' sclab];
elseif nargin==7
   error(err8)
else
   sc=sc;
   % Make sure second optional arg is char
   if ~isstr(sclab)
      error(err7)
   end
   sclab=[' ' sclab];
   scale_xor=scx ;
   scale_yor=scy ;
end
col='k';

%
% save the current value of the current figure's WindowButtonDownFcn,
% WindowButtonMotionFcn, and WindowButtonUpFcn
%
WindowButtonDownFcn=get(gcf,'WindowButtonDownFcn');
WindowButtonMotionFcn=get(gcf,'WindowButtonMotionFcn');
WindowButtonUpFcn=get(gcf,'WindowButtonUpFcn');
set(gcf,'WindowButtonDownFcn','');
set(gcf,'WindowButtonMotionFcn','');
set(gcf,'WindowButtonUpFcn','');


% SCALE VELOCITY DATA TO RENDERED WINDOW SCALE 
%
RLs= get(gca,'XLim');
xr=RLs(2)-RLs(1);
X1=RLs(1);
X2=RLs(2);
RLs= get(gca,'YLim');
yr=RLs(2)-RLs(1);
Y1=RLs(1);
Y2=RLs(2);

% IF RenderLimits NOT SET, USE RANGE OF DATA
%
if(xr==0|yr==0)
   error('Axes must have been previously set for VECPLOT2 to work');
end
pct10=xr/10;

%FILTER DATA THROUGH VIEWING WINDOW
%
filt=find(xin>=X1&xin<=X2&yin>=Y1&yin<=Y2);
x=xin(filt);
y=yin(filt);
u=uin(filt);
v=vin(filt);

% SCALE BY MAX VECTOR SIZE IN U AND V
%
us=u/sc;
vs=v/sc;

% SCALE TO 10 PERCENT OF X RANGE
%
us=us*pct10;
vs=vs*pct10;
 
% SEND VECTORS TO DRAWVEC ROUTINE
%
hp=drawvec(x,y,us,vs,25,col);
set(hp,'UserData',[xin yin uin vin]);
set(hp,'Tag','vectors');

% COLOR LARGEST VECTOR RED
%[trash,imax]=max(sqrt(us.*us+vs.*vs));
%hvmax=drawvec(x(imax),y(imax),us(imax),vs(imax),25,'r');
%set(hvmax,'Tag','scalearrow');

% PLACE SCALE WITH MOUSE ON SCREEN
%
if ~isempty(sclab)
   ptr=get(gcf,'Pointer');
   if ~exist('scale_xor')| ~exist('scale_yor')
      disp('place scale on plot with a mouse button');
      [scale_xor,scale_yor]=ginput(1);
   end 
   
   ht1=drawvec(scale_xor,scale_yor,pct10,0.,25,'r');
   set(ht1,'Tag','scalearrow');
   if strcmp(sclab,'m/s')
      sctext=[num2str(sc) sclab];
   else
      sctext=[num2str(100*sc) sclab];
   end
   scaletext=text((scale_xor+scale_xor+pct10)/2,scale_yor-(Y2-Y1)*(.05),sctext);
   set(scaletext,'HorizontalAlignment','center');
   set(scaletext,'VerticalAlignment','middle');
   set(scaletext,'Tag','scaletext');
   set(gcf,'Pointer',ptr);

else
   ht1=[];scaletext=[];
end

% OUTPUT IF DESIRED
%
if nargout==1,retval=[hp ht1 scaletext];,end



%
% return the saved values of the current figure's WindowButtonDownFcn,
% WindowButtonMotionFcn, and WindowButtonUpFcn to the current figure
%
set(gcf,'WindowButtonDownFcn',WindowButtonDownFcn);
set(gcf,'WindowButtonMotionFcn',WindowButtonMotionFcn);
set(gcf,'WindowButtonUpFcn',WindowButtonUpFcn);

%
%        Brian O. Blanton
%        Department of Marine Sciences
%        15-1A Venable Hall
%        CB# 3300
%        Uni. of North Carolina
%        Chapel Hill, NC
%                 27599-3300
%
%        919-962-4466
%        blanton@marine.unc.edu
%      
%        SUMMER 1998
%