diff chordtools/intervals2quality.m @ 1:8973548174c1 tip

adding tools to repo

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/chordtools/intervals2quality.m	Mon May 06 14:43:47 2013 +0100
@@ -0,0 +1,115 @@
+%
+%INTERVALS2QUALITY Return the quality of a given interval_list
+% 
+% [quality,success, errormessage] = intervals2quality(interval_list, {verbose})
+% 
+% Converts a list of interval strings to an integer value denoting the
+% chord's quality. Quality values are from the enumeration:
+%
+% 0   Major
+% 1   Minor
+% 2   Diminished
+% 3   Augmented
+% 4   Suspended
+%
+% Success = 1 if symbols parsed correctly, 0 otherwise. 
+%
+% If optional argument 'verbose' is 1, function prints any errormessage to 
+% the screen.
+% 
+% calls:    intervals2semitones
+% 
+% returns:  quality (integer)
+%           success  (boolean)  
+%           errormessage (string)
+%
+%
+% Author: Christopher Harte,  March 2009
+% 
+% Copyright: Centre for Digital Music, Queen Mary University of London 2005 
+%
+% This file is part of the C4DM Chord Toolkit V2.0  
+%
+% The C4DM Chord Toolkit is free software; you can redistribute it and/or 
+% modify it under the terms of the GNU General Public License as published 
+% by the Free Software Foundation; either version 2 of the License, or
+% (at your option) any later version.
+%
+% The C4DM Chord Toolkit is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with the C4DM Toolkit; if not, write to the Free Software
+% Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+%
+function [quality,success,errormessage] = intervals2quality(interval_list,verbose)
+
+
+
+
+quality = '';
+errormessage = '';
+
+if nargin < 2
+    verbose = 0;
+end
+
+% define templates for the 5 different triad chords (four quality families
+% plus suspension) - weights mean maj thirds will have more effect than min
+% 3rds which in turn have more effect than 5ths and then 2nds and 4ths
+
+templates = [[1,0,0,0,6,0,0,4,0,0,0,0]; ... % maj
+             [1,0,0,5,0,0,0,4,0,0,0,0]; ... % min
+             [1,0,0,5,0,0,4,0,0,0,0,0]; ... % dim
+             [1,0,0,0,6,0,0,0,4,0,0,0]; ... % aug
+             [1,0,2,0,0,2,0,4,0,0,0,0]];    % sus
+             
+         
+% get the semitone equivalents of the intervals in the interval list             
+[semitones,success,error] = intervals2semitones(interval_list);
+
+indexa = 1;
+
+% initialise a binary vector showing which semitones are present 
+present = zeros(1,12);
+
+while indexa <= 3 && indexa <= length(semitones) 
+    
+    % for each of the first three semitones in the list make its position a
+    % one in the vector 'present' 
+    
+    if semitones(indexa) < 12
+    
+        present(semitones(indexa)+1) = 1;
+    
+    end
+    indexa = indexa +1;
+    
+end
+
+% multiply present by the templates matrix to give a vector of scores for
+% the possible qualities
+qvector = templates * present';
+
+
+% find maximum value from the qualities vector
+% this function benfits from the max function's picking of the first
+% maximum value if there are several equal ones so is predisposed toward 
+% major if the quality is not obvious from the input. (e.g. C:(1) returns major)  
+[value,index] = max(qvector);
+
+% take 1 from index to give correct enumeration
+quality = index-1;
+
+
+if(success==0) 
+
+    errormessage = sprintf([error 'Error in intervals2quality: incorrect interval in list "' interval_list '"\n']);
+    
+    if verbose == 1
+        fprintf(1, errormessage);
+    end
+end