MINTERSECT -- Multiple set intersection.

A generalization of INTERSECT to handle multiple inputs.

Description

MINTERSECT(A,B,C,...) when A,B,C... are vectors returns the values common to all A,B,C... The result will be sorted. A,B,C... can be cell arrays of strings.

MINTERSECT repeatedly evaluates INTERSECT on successive pairs of sets, which may not be very efficient. For a large number of sets, this should probably be reimplemented using some kind of tree algorithm.

MINTERSECT(A,B,'rows') when A,B,C... are matrices with the same number of columns returns the rows common to all A,B,C...

• MATLAB release: MATLAB 6.5 (R13)

[James K]

What 'intersect' should have been. Thanks to the author, very straightforward.

[Claas V]

Useful extension of intersect.m

[Stratis Gavves]

Very handy. Mathworks should already have this functionality in the intersect function.

[Alexander]

Very useful function, thanks. Although it doesn't return indices like usual intersect.
That's actually quite easy. Here's what that function should look like. Please update your submition so other people could use it

function [runIntersect, varargout] = mintersect(varargin)
%MINTERSECT Multiple set intersection.
% MINTERSECT(A,B,C,...) when A,B,C... are vectors returns the values
% common to all A,B,C... The result will be sorted. A,B,C... can be cell
% arrays of strings.
%
% MINTERSECT repeatedly evaluates INTERSECT on successive pairs of sets,
% which may not be very efficient. For a large number of sets, this should
% probably be reimplemented using some kind of tree algorithm.
%
% MINTERSECT(A,B,'rows') when A,B,C... are matrices with the same
% number of columns returns the rows common to all A,B,C...
%
% [C,IA,IB,IC,...] = MINTERSECT(...) returns required number of indices, similar to INTERSECT
%
% See also INTERSECT

flag = 0;
if isempty(varargin),
    error('No inputs specified.')
else
    if isequal(varargin{end},'rows'),
        flag = 'rows';
        setArray = varargin(1:end-1);
    else
        setArray = varargin;
    end
end

nout = min(length(setArray),max(nargout,1)-1);
varargout = cell(nout, 1);
for k = 1:nout
    varargout(k) = {(1:length(setArray{k}))'};
end

runIntersect = setArray{1};
for i = 2:length(setArray),
    
    if isequal(flag,'rows'),
        [runIntersect, i1, i2] = intersect(runIntersect,setArray{i},'rows');
    elseif flag == 0,
        [runIntersect, i1, i2] = intersect(runIntersect,setArray{i});
    else
        error('Flag not set.')
    end
    for k = 2:min(i,nout+1)
        varargout(k-1) = {varargout{k-1}(i1)};
    end
    if k <= nout
        varargout(k) = {i2};
    end
    
    if isempty(runIntersect)
        for k = 1:nout
            varargout(k) = {};
        end
        return
    end
    
end

[Alexander]

One small correction: at the end the line

varargout(k) = {};

should be changed to

varargout(k) = {[]};