sub2indq.m

% Ultralytics 🚀 AGPL-3.0 License - https://ultralytics.com/license

function ndx = sub2indq(siz,varargin)
%SUB2IND Linear index from multiple subscripts.
%   DISABLED ERROR CHECKING FOR FASTER SPEED! JOCHER!!
%   SUB2IND is used to determine the equivalent single index
%   corresponding to a given set of subscript values.
%
%   IND = SUB2IND(SIZ,I,J) returns the linear index equivalent to the
%   row and column subscripts in the arrays I and J for a matrix of
%   size SIZ. 
%
%   IND = SUB2IND(SIZ,I1,I2,...,IN) returns the linear index
%   equivalent to the N subscripts in the arrays I1,I2,...,IN for an
%   array of size SIZ.
%
%   I1,I2,...,IN must have the same size, and IND will have the same size
%   as I1,I2,...,IN. For an array A, if IND = SUB2IND(SIZE(A),I1,...,IN)),
%   then A(IND(k))=A(I1(k),...,IN(k)) for all k.
%
%   Class support for inputs I,J: 
%      float: double, single
%
%   See also IND2SUB.

%   Copyright 1984-2008 The MathWorks, Inc.
%   $Revision: 1.14.4.8 $  $Date: 2008/05/23 15:34:46 $
%==============================================================================

siz = double(siz);
% if length(siz)<2
%         error('MATLAB:sub2ind:InvalidSize',...
%             'Size vector must have at least 2 elements.');
% end

if length(siz) ~= nargin-1
    %Adjust input
    if length(siz)<nargin-1
        %Adjust for trailing singleton dimensions
        siz = [siz ones(1,nargin-length(siz)-1)];
    else
        %Adjust for linear indexing on last element
        siz = [siz(1:nargin-2) prod(siz(nargin-1:end))];
    end
end

%Compute linear indices
k = [1 cumprod(siz(1:end-1))];
ndx = 1;
%s = size(varargin{1}); %For size comparison
for i = 1:length(siz),
    v = varargin{i};
    %%Input checking
%     if ~isequal(s,size(v))
%         %Verify sizes of subscripts
%         error('MATLAB:sub2ind:SubscriptVectorSize',...
%             'The subscripts vectors must all be of the same size.');
%     end
%     if (any(v(:) < 1)) || (any(v(:) > siz(i)))
%         %Verify subscripts are within range
%         error('MATLAB:sub2ind:IndexOutOfRange','Out of range subscript.');
%     end
    ndx = ndx + (v-1)*k(i);
end