77 lines
2.0 KiB
Matlab
77 lines
2.0 KiB
Matlab
function X = randp(P,varargin)
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% RANDP - pick random values with relative probability
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%
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% R = RANDP(PROB,..) returns integers in the range from 1 to
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% NUMEL(PROB) with a relative probability, so that the value X is
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% present approximately (PROB(X)./sum(PROB)) times in the matrix R.
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%
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% All values of PROB should be equal to or larger than 0.
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%
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% RANDP(PROB,N) is an N-by-N matrix, RANDP(PROB,M,N) and
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% RANDP(PROB,[M,N]) are M-by-N matrices. RANDP(PROB, M1,M2,M3,...) or
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% RANDP(PROB,[M1,M2,M3,...]) generate random arrays.
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% RANDP(PROB,SIZE(A)) is the same size as A.
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%
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% Example:
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% R = randp([1 3 2],1,10000)
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% % return a row vector with 10000 values with about 16650% 2
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% histc(R,1:3) ./ numel(R)
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%
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% R = randp([1 1 0 0 1],10,1)
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% % 10 samples evenly drawn from [1 2 5]
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%
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%
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% Also see RAND, RANDPERM
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% RANDPERMBREAK, RANDINTERVAL, RANDSWAP (MatLab File Exchange)
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% Created for Matlab R13+
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% version 2.0 (feb 2009)
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% (c) Jos van der Geest
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% email: jos@jasen.nl
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%
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% File history:
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% 1.0 (nov 2005) - created
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% 1.1 (nov 2005) - modified slightly to check input arguments to RAND first
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% 1.2 (aug 2006) - fixed bug when called with scalar argument P
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% 2.0 (feb 2009) - use HISTC for creating the integers (faster and simplier than
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% previous algorithm)
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error(nargchk(2,Inf,nargin)) ;
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try
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X = rand(varargin{:}) ;
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catch
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E = lasterror ;
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E.message = strrep(E.message,'rand','randp') ;
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rethrow(E) ;
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end
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P = P(:) ;
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if any(P<0),
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error('All probabilities should be 0 or larger.') ;
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end
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if isempty(P) || sum(P)==0
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warning([mfilename ':ZeroProbabilities'],'All zero probabilities') ;
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X(:) = 0 ;
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else
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[junk,X] = histc(X,[0 ; cumsum(P(:))] ./ sum(P)) ;
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end
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% Method used before version 2
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% X = rand(varargin{:}) ;
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% sz = size(X) ;
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% P = reshape(P,1,[]) ; % row vector
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% P = cumsum(P) ./ sum(P) ;
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% X = repmat(X(:),1,numel(P)) < repmat(P,numel(X),1) ;
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% X = numel(P) - sum(X,2) + 1 ;
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% X = reshape(X,sz) ;
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