function [data,nnv,gname]=read_v3r(fname)
%READ_V3R read a FEM output file of .v3r filetype.
%   READ_V3R is part of a suite of OPNML I/O functions  
%   to read specific filetypes pertaining to FEM model  
%   input and output.   These functions allow the user to
%   get these data files into MATLAB without copying the
%   files and removing the header info by hand.
%
%   READ_V3R reads the FEM filetype .v3r, as 
%   detailed in "Data File Standards for the Gulf of Maine
%   Project" from the Numerical Methods Laboratory at 
%   Dartmouth College.  There are five
%   columns, the first of which is the node number.  The
%   remaining columns are floating point.  The filetype 
%   suffix ('.v3r') must be included in the input file name. 
%
%   Input :   If fname is omitted, READ_V3R enables a file browser
%             with which the user can specify the .v3r file.
%
%             Otherwise, fname is the name of the file, relative or 
%             absolute (fullpath), including the suffix '.v3r'.
%             This input is a string so it must be enclosed in single 
%             quotes. The comment line is discarded.
%
%  Output :   Call READ_V3R as:
%             >> [data,nnv,gname]=read_v3r(fname);
%             The domain name will be returned in "gname".
%             The number of vertical nodes is returned in "nnv".
%             The node counter, depth and amplitudes  of the u,
%             v, and w components of the vector field are returned 
%             in "data".
%
%             If READ_V3R cannot locate the file, it exits, returning 
%             a -1 instead of the data matrix.
%
%   NOTES :   The v3r filetype contains 3-D data; i.e., real-valued
%             velocity data at each vertical node per horizontal node.
%             
% Call as: [data,nnv,gname]=read_v3r(fname);
%
% Written by : Brian O. Blanton
%

if nargin==0 & nargout==0
   disp('Call as: [data,nnv,gname]=read_v3r(fname);')
   return
end

if ~exist('fname')
   [fname,fpath]=uigetfile('*.v3r','Which .v3r ?');
   if fname==0,return,end
else
   fpath=[];
end

% get filetype from tail of fname
ftype=fname(length(fname)-2:length(fname));

% make sure this is an allowed filetype
if ~strcmp(ftype,'v3r')
   error(['READ_V3R cannot read ' ftype ' filetype'])
end

% open fname
[pfid,message]=fopen([fpath fname]);
if pfid==-1
   error([fpath fname,' not found. ',message]);
end

% In all filetypes there is always a gridname and description line
% as lines #1 and #2 of the file.
% read grid name from top of file; header line #1
gridname=fgets(pfid);
gname=blank(gridname);

% read description line from top of file; header line #2
descline=fgets(pfid);

% read number of vertical nodes (line #3) 
nnv=fscanf(pfid,'%d',1);

% read data segment 
data=fscanf(pfid,'%d %f %f %f %f',[5 inf])';
fclose(pfid);
%
%        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
%