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Commit 913d03c6 authored by Keyser, Johannes's avatar Keyser, Johannes
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add unchanged code+license from File Exchange

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function [m, b] = TheilSen(data)
% Performs Theil-Sen robust linear regression on data
%
% [m b] = TheilSen(data)
%
% data: A MxD matrix with M observations. The first D-1 columns are the
% explanatory variables and the Dth column is the response such that
% data = [x1, x2, ..., x(D-1), y];
%
% m: Estimated slope of each explanatory variable with respect to the
% response varuable. Therefore, m will be a vector of D-1 slopes.
% b: Estimated offsets.
%
%
% EXAMPLE:
% -------
% n=100;
% outN=round(0.2*n);
% noise = randn(n,2)*0.1; noise(randi(n*2,[outN 1]))=randn(outN,1)*5;
% data = [linspace(0,10,n)' linspace(0,5,n)'] + noise;
% Bhat = [ones(n,1) data(:,1)]\data(:,2);
% [m, b] = TheilSen(data);
% plims = [min(data(:,1)) max(data(:,1))]';
% figure
% plot(data(:,1),data(:,2),'k.',...
% plims,plims*m+b,'-r',...
% plims,plims*Bhat(2)+Bhat(1),'-b','linewidth',2)
% legend('Data','TheilSen','Least Squares','location','NW')
% title(sprintf('Acual Slope = %2.3g, LS est = %2.3g, TS est = %2.3g',[0.5 Bhat(2) m]))
%
%
% Source:
% Gilbert, Richard O. (1987), "6.5 Sen's Nonparametric Estimator of
% Slope", Statistical Methods for Environmental Pollution Monitoring,
% John Wiley and Sons, pp. 217�219, ISBN 978-0-471-28878-7
%
%
%
% %%% Z. Danziger October 2014 %%%
% edits Z. Danziger September 2015:
% - updated help
% - speed increase for 2D case
%
%
sz = size(data);
if length(sz)~=2 || sz(1)<2
error('Expecting MxD data matrix with at least 2 observations.')
end
if sz(2)==2 % normal 2-D case
C = nan(sz(1));
for i=1:sz(1)
% accumulate slopes
C(i,i:end) = (data(i,2)-data(i:end,2))./(data(i,1) - data(i:end,1));
end
m = nanmedian(C(:)); % calculate slope estimate
if nargout==2
b = nanmedian(data(:,2)-m*data(:,1)); % calculate intercept if requested
end
else % other cases
C = nan(sz(1),sz(2)-1,sz(1));
for i=1:sz(1)
C(:,:,i) = bsxfun( @rdivide,data(i,end)-data(:,end),...
bsxfun(@minus,data(i,1:end-1),data(:,1:end-1)) ); % accumulate slopes
end
Cprm = reshape( permute(C,[1 3 2]), [],size(C,2),1 ); % stack layers of C to 2D
m = nanmedian(Cprm,1); % calculate slope estimate
if nargout==2
% calculate all intercepts if requested
b = nanmedian( bsxfun(@minus,data(:,end),bsxfun(@times,m,data(:,1:end-1))) );
end
end
Copyright (c) 2015, Zachary Danziger
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the distribution
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
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