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# hist_update

## PURPOSE

'hist_update': update of a current global histogram by inclusion of a new field

## SYNOPSIS

function [val,HIST]=hist_update(val,HIST,C,dC)

## DESCRIPTION

    '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.

## CROSS-REFERENCE INFORMATION

This function calls:

This function is called by:

## SOURCE CODE

    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;