binlookup

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function i = binlookup(idx, omega, tau, idx0)

%BINLOOKUP For a given index, determine its appropriate bin.
%
%   I = BINLOOKUP(K,OMEGA,TAU,K0) returns the bin number of index K, where
%   the bins are defined by paramtesr TAU, OMEGA, and K0. The parameters
%   TAU, OMEGA, and K0 are  optional. If they are not defined or defined as
%   an emptyset ([]), then they take on the default values, which are
%   OMEGA=2, TAU=1, K0=1.
%
%   Note: If K is a vector, than I is a vector of bins.
%
%   See also BINSTART, BINDATA.
%
% Tamara G. Kolda, Ali Pinar, and others, FEASTPACK v1.1, Sandia National
% Laboratories, SAND2013-4136W, http://www.sandia.gov/~tgkolda/feastpack/,
% January 2014

License

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 HOLDER 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.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

% **
if ~exist('omega','var') || isempty(omega)
    omega = 2;
end

if ~exist('tau','var') || isempty(tau)
    tau = 1;
end

if ~exist('idx0','var') || isempty(idx0)
    idx0 = 1;
end

% **
if any(idx < idx0)
    error('Index is smaller than the start of the first bin');
end

n = length(idx);
i = zeros(n,1);
for k = 1:n
    if (idx(k)-idx0+1) < tau
        i(k) = idx(k)-idx0+1;
    else
        tmp = 1 + (omega-1)*(idx(k)-idx0+1 - tau);
        i(k) = floor(log(tmp)/log(omega)) + tau ;
    end
end

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