hist_update

'hist_update': update of a current global histogram by inclusion of a new field
------------------------------------------------------------------------
[val,HIST]=hist_update(val,HIST,C,dC)

 OUTPUT:
 val: vector of field values at which the histogram is determined (middle of bins)
 HIST(:,icolor): nbre of occurence of the field value in the bins whose middle is given by val
           can be a column vector, same size as val, or a matrix with three columns, for color images

 INPUT:
 val: existing field values from the current histogram, =[] if there is no current histogram
 HIST(:,icolor): current histogram,  =[] if there is none
       can be a column vector (icolor=1), same size as val, or a matrix with three columns, for color images      
 C(:,icolor): vector representing the current field values
       can be a column vector (icolor=1), or a matrix with three columns, for color images 
 dC: width of the new bins extending val to account for the new field.

0001 %'hist_update': update of a current global histogram by inclusion of a new field
0002 %------------------------------------------------------------------------
0003 %[val,HIST]=hist_update(val,HIST,C,dC)
0004 %
0005 % OUTPUT:
0006 % val: vector of field values at which the histogram is determined (middle of bins)
0007 % HIST(:,icolor): nbre of occurence of the field value in the bins whose middle is given by val
0008 %           can be a column vector, same size as val, or a matrix with three columns, for color images
0009 %
0010 % INPUT:
0011 % val: existing field values from the current histogram, =[] if there is no current histogram
0012 % HIST(:,icolor): current histogram,  =[] if there is none
0013 %       can be a column vector (icolor=1), same size as val, or a matrix with three columns, for color images
0014 % C(:,icolor): vector representing the current field values
0015 %       can be a column vector (icolor=1), or a matrix with three columns, for color images
0016 % dC: width of the new bins extending val to account for the new field.
0017 
0018 function [val,HIST]=hist_update(val,HIST,C,dC)
0019 
0020 valplus=[];valminus=[];
0021 HISTplus=[];HISTminus=[];
0022 if isempty(HIST)
0023     HIST=0;
0024 end
0025 siz=size(C);nbfields=siz(2);
0026 C=double(C);
0027 valmin=min(val); 
0028 valmax=max(val);
0029 Cmin=min(min(C)); Cmax=max(max(C));
0030 if isempty(val)%no current histogram
0031     val=[Cmin-dC/2:dC:Cmax+dC/2];
0032 else %extending the current histogram beyond its maximum value
0033     if Cmax>=valmax+dC/2;
0034         valplus=[valmax+dC:dC:Cmax+dC/2];% we extend the values val
0035         HISTplus=zeros(length(valplus),nbfields);% we put histogram to zero at these values
0036     end
0037     %extending the current histogram below its minimum value
0038     if Cmin<=valmin-dC/2;
0039         valminus=[valmin-dC:-dC:Cmin-dC/2];% we extend the values val
0040         valminus=sort(valminus);% we reverse the order
0041         HISTminus=zeros(length(valminus),nbfields);% we put histogram to zero at these values
0042     end
0043     val=[valminus val valplus];
0044 end
0045 HIST=[HISTminus;HIST;HISTplus];
0046 if nbfields==1
0047     histC=(hist(C,val))';% initiate the global histogram
0048 elseif nbfields==3
0049     HIST1=(hist(C(:,1),val))';
0050     HIST2=(hist(C(:,2),val))';
0051     HIST3=(hist(C(:,3),val))';
0052     histC=[HIST1 HIST2 HIST3];
0053 end
0054 HIST=HIST+histC;