%   Label object
%   
%   In order for it to work all the functions must be in a directory named @label present the pathdef.m file (i.e. in the MatLab searching path).
%   
%   The purpose of the label object is to provide a simple tool handling the labels (and some other information) of a certain data set in a given mode.
%   
%   The label object is created by means of the function label
%   
%   SYNTAX
%   
%   Labels = label(Lab,DefLab,Scalars,AxisLabels,Name,MeasUn)
%   
%    Lab:         can be char array or cell vector of chars or vector of doubles. In the latter case 
%                 the labels are in the form [DefLab number]. If scalars is defined this field is not necessary
%    DefLab:      default: 'Var.'
%    Scalars:     scalars to plot against. If Lab is empty the labels are in the form [scalar MeasUn], if not defined
%                 Scalars = 1:length(Lab)
%    MeasUn:      default: ''
%    AxisLabels:  char array or cell vector of arrays
%    Name:        name of the label object
%   
%   
%   A label object can refer to any dimension in a multidimensional array. 
%   Only a few functions are defined on the label object:
%   1. char.m       transforms the label object into a char array    
%   2. display.m    this function is used to display the content of a label object 
%   3. end.m        it is used to allow the use of "end" in subsref and subsasgn
%   4. length.m     returns the number of labels of the labels object
%   5. size.m       returns the number of labels in the first mode and 1 in the second mode, multidimensional label objects are
%   		not allowed
%   6. subsasgn.m   allows to assign values to certain parts of the label object (such as labels, scalars...)
%   7. subsindex.m  since the label object cannot be used as an index for other matrices it simply returns an error message
%   8. subsref.m    allows to refer to subsets of labels. Its output is a new label object or variables belonging to a suitable
%   		class (such as cell arrays, char arrays, etc.)
%   
%   Examples:
%   
%   Assuming that one has a data set of dimensions 20 x 4 x 10, where the first dimension represents the samples, the second the concentration of 4 different compounds and the third the measurement times (from 1 to 28 seconds every third second).
%   One can than create three label objects respectively having length 20, 4 and 10.
%   
%   »Lab1 = label(1:20,'Sam',[],'Samples','Samples');
%   »Lab2 = label({'Tryptophan','DOPA','Tyrosine','Phenilalanine'},'Comp.',[],'Compounds','Compounds');
%   »Lab3 = label([],'',1:3:28,'Time (s)','Time','s');
%   »Lab1,Lab2,Lab3 
%   
%   Name      : Samples
%   Meas. unit: 
%   Def. label: Sam 
%   Axis label: Samples
%   Labels    : Sam 1 
%               Sam 2 
%               Sam 3 
%               Sam 4 
%               Sam 5 
%               Sam 6 
%               Sam 7 
%               Sam 8 
%               Sam 9 
%               Sam 10
%               Sam 11
%               Sam 12
%               Sam 13
%               Sam 14
%               Sam 15
%               Sam 16
%               Sam 17
%               Sam 18
%               Sam 19
%               Sam 20
%   
%   Name      : Compounds
%   Meas. unit: 
%   Def. label: Comp. 
%   Axis label: Compounds
%   Labels    : Tryptophan   
%               DOPA         
%               Tyrosine     
%               Phenilalanine
%               
%   Name      : Time
%   Meas. unit: s
%   Def. label:  
%   Axis label: Time (s)
%   Labels    : 1 s 
%               4 s 
%               7 s 
%               10 s
%               13 s
%               16 s
%               19 s
%               22 s
%               25 s
%               28 s
%   
%   The label object can be treated as a normal vector: 
%   
%   » t = Lab1(1:2:end) 
%   
%   Name      : Samples
%   Meas. unit: 
%   Def. label: Sam  
%   Axis label: Samples
%   Labels    : Sam 1 
%               Sam 3 
%               Sam 5 
%               Sam 7 
%               Sam 9 
%               Sam 11
%               Sam 13
%               Sam 15
%               Sam 17
%               Sam 19
%   
%   and t is a 10 x 1 label object:
%   » whos t
%     Name      Size         Bytes  Class
%   
%     t        10x1           2116  label object
%   
%   Grand total is 103 elements using 2116 bytes
%   
%   To access labels, scalars and the other properties of the label object one can use a dot as for structures:
%   
%   » Lab1.labels
%   
%   ans = 
%   
%       'Sam 1'
%       'Sam 2'
%       'Sam 3'
%       'Sam 4'
%       'Sam 5'
%       'Sam 6'
%       'Sam 7'
%       'Sam 8'
%       'Sam 9'
%       'Sam 10'
%       'Sam 11'
%       'Sam 12'
%       'Sam 13'
%       'Sam 14'
%       'Sam 15'
%       'Sam 16'
%       'Sam 17'
%       'Sam 18'
%       'Sam 19'
%       'Sam 20'
%       
%   » Lab3.scalars
%   
%   ans =
%   
%        1
%        4
%        7
%       10
%       13
%       16
%       19
%       22
%       25
%       28
%   
%   » Lab2.axislabels
%   
%   ans = 
%   
%       'Compounds'
%   
%   » Lab2.deflab
%   
%   ans =
%   
%   Comp. 
%   
%   » Lab2.name
%   
%   ans =
%   
%   Compounds
%   
%   Complex constructions are also allowed for reference, e.g.
%   
%   » Lab1(1:2:end).labels
%   
%   ans = 
%   
%       'Sam 1'
%       'Sam 3'
%       'Sam 5'
%       'Sam 7'
%       'Sam 9'
%       'Sam 11'
%       'Sam 13'
%       'Sam 15'
%       'Sam 17'
%       'Sam 19'
%   
%   The scalars and the labels are kept together:
%   
%   » p = Lab3(1:5)
%   Name      : Time
%   Meas. unit: s
%   Def. label:   
%   Axis label: Time (s)
%   Labels    : 1 s 
%               4 s 
%               7 s 
%               10 s
%               13 s
%   
%   » p.scalars
%   
%   ans =
%   
%        1
%        4
%        7
%       10
%       13
%   
%   The "Def. label" (default label) is used to reconstruct undefined labels:
%   » Lab(11:15)=Lab1(1:5)
%   yields
%   Name      : 
%   Meas. unit: 
%   Def. label: Var. 
%   Axis label: 
%   Labels    : Var. 1 
%               Var. 2 
%               Var. 3 
%               Var. 4 
%               Var. 5 
%               Var. 6 
%               Var. 7 
%               Var. 8 
%               Var. 9 
%               Var. 10
%               Sam 1  
%               Sam 2  
%               Sam 3  
%               Sam 4  
%               Sam 5  
%   
%   because the standard value for "Def. label" is 'Var.' and Lab is an empty undefined matrix
%   
%   » Lab1(25)='Sample 30'
%    
%   Name      : Samples
%   Meas. unit: 
%   Def. label: Sam 
%   Axis label: Samples
%   Labels    : Sam 1    
%               Sam 2    
%               Sam 3    
%               Sam 4    
%               Sam 5    
%               ...
%               ...
%               Sam 20   
%               Sam 21   
%               Sam 22   
%               Sam 23   
%               Sam 24   
%               Sample 30
%   
%   Because "Def. label" for Lab1 is 'Sam' the labels between 21 and 24 are created automatically.
%   The assigned value can either be a char array, a cell vector containing only strings or another label object. 
%   E.g.:
%   » t={'Fluoranthene','Nonylphenol'}'
%   » Lab2(6:7)=t
%    
%   Name      : Compounds
%   Meas. unit: 
%   Def. label: Comp. 
%   Axis label: Compounds
%   Labels    : Tryptophan   
%               DOPA         
%               Tyrosine     
%               Phenilalanine
%               Comp. 5      
%               Fluoranthene 
%               Nonylphenol  
%   Since "Def. label" for Lab2 is 'Comp.'. Note that t must be a column cell vector otherwise the operation will return the original label object
%   There is no filling in for the scalars themselves, which are instead turned automatically to 1:length(label) in case the filling for the labels by means of "Def. label" is applied. Hence if one defines the labels by scalars it is basically not possible to update the label object without updating all the scalars at the same time, otherwise all the scalars are lost:
%   » Lab3.scalars = [2:3:29]
%    
%   Name      : Time
%   Meas. unit: s
%   Def. label:   
%   Axis label: Time (s)
%   Labels    : 2 s 
%               5 s 
%               8 s 
%               11 s
%               14 s
%               17 s
%               20 s
%               23 s
%               26 s
%               29 s
%    
%   There is an automatic check for identical labels and scalars, if any the operation is interrupted and an error message is generated:
%   » Lab1(2)='Sam 1'
%   ??? Error using ==> label/subsasgn
%   No label or scalar can be repeated
%   
%   The length on the two sides of an assignment must be the same:
%   » Lab3.scalars = [2:3:22]
%   ??? Error using ==> label/subsasgn
%   Unequal lengths
%   
%   If one redefines one or more of the actual labels of a label object defined by scalars, the automatic label update based on the automatic scheme [number measurement-unit] stops working hence upon modification the labels remain the same:
%   
%   » Lab3(1)='Null'
%    
%   Name      : Time
%   Meas. unit: s
%   Def. label:   
%   Axis label: Time (s)
%   Labels    : Null
%               5 s 
%               8 s 
%               11 s
%               14 s
%               17 s
%               20 s
%               23 s
%               26 s
%               29 s
%   
%   » Lab3.scalars = 1:3:28
%    
%   Name      : Time
%   Meas. unit: s
%   Def. label:    
%   Axis label: Time (s)
%   Labels    : Null
%               5 s 
%               8 s 
%               11 s
%               14 s
%               17 s
%               20 s
%               23 s
%               26 s
%               29 s
%               
%   Used in: Content object, CBDataSet object
%   Accepted as input in MarkLab object
%   
%   

