errorbar2

 function f = errorbar2(x,y,er,direction,varargin)

 <x>,<y>,<er> are row vectors of the same length
   if <er> has imaginary numbers (determined via any(imag(<er>)~=0)),
   then real(<er>) and imag(<er>) determines the downward and 
   upward (or leftward and rightward) extent of the error bars,
   respectively.  <er> can also be 2 x N where the first row
   has values for the lower bound and the second row has values
   for the upper bound.
 <direction> is
   0 or 'h' or 'x' means error on x
   1 or 'v' or 'y' means error on y
 <varargin> are additional arguments to plot.m (e.g. 'r-')

 draws error lines on the current figure, returning
 a vector of handles.

 example:
 figure; errorbar2(randn(1,10),randn(1,10),randn(1,10)/4,1,'r-');

 TODO: what about the cases of NaNs?  e.g. see errorbar3.m.

0001 function f = errorbar2(x,y,er,direction,varargin)
0002 
0003 % function f = errorbar2(x,y,er,direction,varargin)
0004 %
0005 % <x>,<y>,<er> are row vectors of the same length
0006 %   if <er> has imaginary numbers (determined via any(imag(<er>)~=0)),
0007 %   then real(<er>) and imag(<er>) determines the downward and
0008 %   upward (or leftward and rightward) extent of the error bars,
0009 %   respectively.  <er> can also be 2 x N where the first row
0010 %   has values for the lower bound and the second row has values
0011 %   for the upper bound.
0012 % <direction> is
0013 %   0 or 'h' or 'x' means error on x
0014 %   1 or 'v' or 'y' means error on y
0015 % <varargin> are additional arguments to plot.m (e.g. 'r-')
0016 %
0017 % draws error lines on the current figure, returning
0018 % a vector of handles.
0019 %
0020 % example:
0021 % figure; errorbar2(randn(1,10),randn(1,10),randn(1,10)/4,1,'r-');
0022 %
0023 % TODO: what about the cases of NaNs?  e.g. see errorbar3.m.
0024 
0025 % hold on
0026 prev = ishold;
0027 hold on;
0028 
0029 % prep er
0030 if size(er,1) == 2
0031   switch direction
0032   case {0 'h' 'x'}
0033     er = x - er(1,:) + j*(er(2,:) - x);
0034   case {1 'v' 'y'}
0035     er = y - er(1,:) + j*(er(2,:) - y);
0036   end
0037 end
0038 
0039 % calc
0040 isimag = any(imag(er)~=0);
0041 
0042 % do it
0043 f = [];
0044 if isimag
0045   switch direction
0046   case {0 'h' 'x'}
0047     for p=1:numel(x)
0048       f = [f plot([x(p)-real(er(p)) x(p)+imag(er(p))],[y(p) y(p)],varargin{:})];
0049     end
0050   case {1 'v' 'y'}
0051     for p=1:numel(x)
0052       f = [f plot([x(p) x(p)],[y(p)-real(er(p)) y(p)+imag(er(p))],varargin{:})];
0053     end
0054   otherwise
0055     error('invalid <direction>');
0056   end
0057 else
0058   switch direction
0059   case {0 'h' 'x'}
0060     for p=1:numel(x)
0061       f = [f plot([x(p)-er(p) x(p)+er(p)],[y(p) y(p)],varargin{:})];
0062     end
0063   case {1 'v' 'y'}
0064     for p=1:numel(x)
0065       f = [f plot([x(p) x(p)],[y(p)-er(p) y(p)+er(p)],varargin{:})];
0066     end
0067   otherwise
0068     error('invalid <direction>');
0069   end
0070 end
0071 
0072 % hold off
0073 if ~prev
0074   hold off;
0075 end