time   calls  line
                  1 function y = detrend(x,o,bp)
                  2 %DETREND Remove a linear trend from a vector, usually for FFT processing.
                  3 %   Y = DETREND(X) removes the best straight-line fit linear trend from the
                  4 %   data in vector X and returns the residual in vector Y.  If X is a
                  5 %   matrix, DETREND removes the trend from each column of the matrix.
                  6 %
                  7 %   Y = DETREND(X,'constant') removes just the mean value from the vector X,
                  8 %   or the mean value from each column, if X is a matrix.
                  9 %
                 10 %   Y = DETREND(X,'linear',BP) removes a continuous, piecewise linear trend.
                 11 %   Breakpoint indices for the linear trend are contained in the vector BP.
                 12 %   The default is no breakpoints, such that one single straight line is
                 13 %   removed from each column of X.
                 14 %
                 15 %   Class support for inputs X,BP:
                 16 %      float: double, single
                 17 %
                 18 %   See also MEAN
                 19 
                 20 %   Copyright 1984-2006 The MathWorks, Inc. 
                 21 %   $Revision: 1.9.4.4 $  $Date: 2010/08/23 23:07:35 $
                 22 
            36   23 if nargin < 2, o  = 1; end 
            36   24 if nargin < 3, bp = 0; end 
                 25 
            36   26 n = size(x,1); 
            36   27 if n == 1, 
                 28   x = x(:);			% If a row, turn into column vector
                 29 end
            36   30 N = size(x,1); 
                 31 
            36   32 switch o 
            36   33 case {0,'c','constant'} 
                 34   y = x - ones(N,1)*mean(x);	% Remove just mean from each column
                 35 
            36   36 case {1,'l','linear'} 
  0.01      36   37   bp = unique([0;double(bp(:));N-1]);	% Include both endpoints 
            36   38   lb = length(bp)-1; 
                 39   % Build regressor with linear pieces + DC
            36   40   a  = [zeros(N,lb,class(x)) ones(N,1,class(x))]; 
            36   41   for kb = 1:lb 
            36   42     M = N - bp(kb); 
  0.01      36   43     a((1:M)+bp(kb),kb) = (1:M)'/M; 
            36   44   end 
  0.70      36   45   y = x - a*(a\x);		% Remove best fit 
                 46 
                 47 otherwise
                 48   % This should eventually become an error.
                 49   warning(message('MATLAB:detrend:InvalidTrendType', num2str( o )));
                 50   y = detrend(x,1,bp); 
                 51 
                 52 end
                 53 
            36   54 if n == 1 
                 55   y = y.';
                 56 end