The unchecked module "mfind_" of the Mastrave modelling library
Copyright © 2005,2006,2007,2009,2010 Daniele de Rigo
The file mfind_.m is part of Mastrave.
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[ match_id , val_id , ... ] = mfind_( matches , values , at_most = inf , mode = 'first' )
Find indices and values of those elements of values that are equal
to any element of matches .
This function extends the find(.) function. If matches is a scalar
variable m , find(.) and mfind_(.) behave equivalently using the
id = find( m == values )
id = mfind_( m , values ) If m is not scalar, only mfind_(.) notation is able to scale up to the vectorial case.
If more than one output are assigned, the behavior is analogous to that of the find(.) function, with the relevant exception that the output arguments equivalent to those of find(.) are always preceded by match_id which is a vector containing the position of each element of matches matching with (equal to) at least an element of values .
If matches is a scalar variable m , with find(.) it is possible
to find non matching elements of values by using the notation:
nonmatching_id = find( m ~= values ) which is equivalent to:
nonmatching_id = find( m ~= values , inf , 'first' ) The equivalent notation using mfind_(.) is:
nonmatching_id = mfind_( m , values , inf , 'nfirst' ) Again, if m is not scalar only mfind_(.) notation is able to scale up to the vectorial case. When passing 'nfirst' or 'nlast' criteria as mode , the i-th element of val_id is the position of the values element which is closer to the i-th element of match_id (i.e. the i-th non-matching element of matches ).
matches ::numstring,vector:: Array of numbers or of characters whose elements are to be matched in values . values ::numstring:: Matrix of numbers or of characters in which to find elements matching any of those contained in matches . at_most ::scalar_numel:: Maximum number of matching elements to find in values . (Default: inf ). mode ::string:: Criterion for extracting from values at_most matching elements. (Default: 'first'). Valid modes are: mode │ meaning ─────────────┼───────────────────────────── 'first' │ Returns the first at_most │ matching elements of │ matches against values . ─────────────┼───────────────────────────── 'last' │ Returns the last at_most │ matching elements of │ matches against values . ─────────────┼───────────────────────────── 'nfirst' │ Returns the first at_most │ non-matching elements of │ matches against values . ─────────────┼───────────────────────────── 'nlast' │ Returns the last at_most │ non-matching elements of │ matches against values . Implementation limits: values and matches cannot have more unique values than the maximum integer (intmax, usually 2^31 ─ 1).
% Performance against find(.) n = 300; N = n*n; A = reshape( 1:N , n , n ); p = primes( N ); tic; [ which_p , r1 , c1 ] = mfind_( p , A ); toc tic; r2 = zeros(numel(p),1); c2 = r2; for i=1:numel(p) [ r2(i), c2(i) ] = find( p(i) == A ); end toc all( r1 == r2 ) all( c1 == c2 ) hist( c1 , n ) % Dealing with strings t = 'mfind_( matches, values )' ; [which_punct, indexes] = mfind_( '(,)' , t ) [which_punct, rows, cols] = mfind_( '(,)' , t ) [which_punct, rows, cols, val] = mfind_( '(,)' , t ) t( t == ' ' ) = ; % erase spaces [which_punct, rows, cols, val] = mfind_( '(,)' , t ) t( cols ) = ; % erase separators len = diff([0 cols])-1; % token length tokens = mat2cell( t , 1 , len ) % Finding matches inside a matrix of values V = zeros( 5 , 4 ); nV = numel( V ); rnd = ceil( 99 * rand( 1 , nV ) ) / 10; V(:) = rnd( ceil( rand( 1 , nV ) * numel(rnd) ) ) m = rnd( ceil( rand( 1 , 8 ) * numel(rnd) ) ) [ mpos , Vpos ] = mfind_( m , V ) [ mpos , Vpos ] = mfind_( m , V , 3 ) all( m( mpos(:).' ) == V( Vpos(:)' ) ) [ mpos , r , c , v ] = mfind_( m , V , 3, 'first') all( V( Vpos ) == v ) all( V( Vpos ) == V( sub2ind( size(V) , r , c ) ) ) [ mpos , r , c , v ] = mfind_( m , V , 3, 'last') % Finding non-matching matches [ mpos , Vpos ] = mfind_( m , V , inf, 'nfirst') [ mpos , r , c , v ] = mfind_( m , V , inf, 'nfirst') all( V( Vpos ) == v ) all( V( Vpos ) == V( sub2ind( size(V) , r , c ) ) ) % Check Vpos against the loop version of the algorithm Vpos2 =  for i=1:numel(m) [ dist , pos ] = min( abs( m(i) - V(:) ) ); if dist ~= 0 Vpos2( end+1 ) = pos; end end all( Vpos == Vpos2 ) [ mpos , Vpos ] = mfind_( m , V , 3, 'nlast') [ mpos , r , c , v ] = mfind_( m , V , 3, 'nlast') all( V( Vpos ) == v ) all( V( Vpos ) == V( sub2ind( size(V) , r , c ) ) )
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