function msg = checkpvpairs(pvpairs,linestyle)
%CHECKPVPAIRS Check length of property value pair inputs
%   MSG = CHECKPVPAIRS(PAIRS) returns an error message if the
%   length of the supplied cell array of property value pairs is
%   incorrect. The message is tailored to accepting LINESPEC as an
%   option convenience input argument.

%   Copyright 1984-2003 The MathWorks, Inc. 

msg = '';
npvpairs = length(pvpairs)/2;
if nargin == 1, linestyle = true; end
if (length(pvpairs) == 1) && linestyle
  msg = struct('message','Error in color/linetype argument.',...
               'identifier',id('UnrecognizedLineStyleParameter'));
elseif npvpairs ~= fix(npvpairs)
  msg = struct('message','Incorrect number of inputs for property-value pairs.',...
               'identifier',id('EvenPropValuePairs'));
end

function str = id(str)
str = ['MATLAB:checkpvpairs:' str];