Cedric Roux
56c66c09aa
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52 lines
1.7 KiB
Matlab
52 lines
1.7 KiB
Matlab
function r = ricernd(v, s)
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%RICERND Random samples from the Rice/Rician probability distribution.
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% r = ricepdf(v, s) returns random sample(s) from the Rice (aka Rician)
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% distribution with parameters v and s.
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% (either v or s may be arrays, if both are, they must match in size)
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%
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% R ~ Rice(v, s) if R = sqrt(X^2 + Y^2), where X ~ N(v*cos(a), s^2) and
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% Y ~ N(v*sin(a), s^2) are independent normal distributions (any real a).
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% Note that v and s are *not* the mean and standard deviation of R!
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%
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% The size of Y is the common size of the input arguments. A scalar
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% input functions as a constant matrix of the same size as the other
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% inputs.
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%
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% Note, to add Rician noise to data, with given s and data-dependent v:
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% new = ricernd(old, s);
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%
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% Reference: http://en.wikipedia.org/wiki/Rice_distribution (!)
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%
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% Example:
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%
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% % Compare histogram of random samples with theoretical PDF:
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% v = 4; s = 3; N = 1000;
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% r = ricernd(v*ones(1, N), s);
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% c = linspace(0, ceil(max(r)), 20);
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% w = c(2); % histogram bin-width
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% h = histc(r, c); bar(c, h, 'histc'); hold on
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% xl = xlim; x = linspace(xl(1), xl(2), 100);
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% plot(x, N*w*ricepdf(x, v, s), 'r');
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%
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% See also RICEPDF, RICESTAT.
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% Missing (?) 'See also's RICECDF, RICEFIT, RICEINV, RICELIKE
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% Inspired by normpdf from the MATLAB statistics toolbox
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% Copyright 2007 Ged Ridgway (Ged at cantab dot net)
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if isscalar(v)
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dim = size(s);
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elseif isscalar(s)
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dim = size(v);
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elseif all(isequal(size(v), size(s)))
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% (both non-scalar, matching)
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dim = size(v); % == size(s)
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else
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error('ricernd:InputSizeMismatch','Sizes of s and v inconsistent.')
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end
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x = s .* randn(dim) + v;
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y = s .* randn(dim);
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r = sqrt(x.^2 + y.^2);
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