histnorm.m

function varargout = histnorm(varargin)
% HISTNORM Histogram normalized
%   [...] = HISTNORM(...) works like HIST, but the frequency is normalized
%   so that area sum is 1.
%
%   Bonus usage!
%   [...] = HISTNORM(..., 'plot') plots and returns the output arguments. 
%   Be sure 'plot' is the last argument.
%
%   Example:
%       data = randn (10000, 1);
%       [xo,no] = histnorm(data, 101, 'plot');
%       hold on
%       plot (no, normpdf(no), 'r');
%       hold off
%
%   See also: HIST.

%   Copyright 2009 DWTFYW.

% check whether plot is done
doPlot = 0;
if ischar (varargin{end}) && strcmpi ('plot', varargin{end})
    doPlot = 1;
    varargin = varargin(1:end-1);
elseif nargout == 0
    doPlot = 1;    
end

% normalize so the "area" is 1
[xo,no] = hist (varargin{:});
binwidths = diff ([min(varargin{1}) no(1:end-1)+diff(no)/2 max(varargin{1})]);
xonorm = xo/sum (xo .* binwidths);
varargout = {xonorm, no};
varargout = varargout(1:nargout);

% do plot
if doPlot
    cax = axescheck(varargin{:});

%     % bored way: bar plot
%     if isempty (cax)
%         bar (no, xonorm, 'hist');
%     else
%         bar (cax, no, xonorm, 'hist');
%     end
    
    % funny way: modify vertices of bar plot
    hist (varargin{:});
    if isempty (cax)
        cax = gca;
    end
    ch = findobj (get (cax, 'children'), 'type', 'patch'); ch = ch(1);
    vertices = get (ch, 'vertices');
    for idx = 1:numel (xonorm)
        vertices((idx-1)*5+[3 4],2) = xonorm(idx);     % hope it works :)
    end
    set (ch, 'vertices', vertices);
end