function [levels, histogram, bins] = statelevels (x, varargin) // defining function
    
    // This function estimate statelevels of real vector X via histogram.
    // Calling Sequence
    // levels=statelevels(x, nbins, method, bounds)
    // [levels histogram]=statelevels(x, nbins, method, bounds)
    // [levels histogram bins]=statelevels(x, nbins, method, bounds)  
    // [levels histogram bins]=statelevels(x, nbins, method, bounds, 'fig', On or Off)  
    // Parameters
    // x: real vector
    // nbins: number of histogram bins to use in the histogram as a positive scalar, where the default value is 100
    // method: method to estimate the statelevels using specified METHOD as one of 'mean' or 'mode', where the  default value is 'mode'
    // bounds: specify the lower and upper bound for the histogram as a two-element row vector
    // fig: specify the logical input value to display figure as one of 'on' or 'off', where the default input in 'off'.
    // levels: return lower and upper level values
    // histogram: return histogram values
    // bins: return binlevels values
    // Examples
    // x=[1.2, 5, 10, -20, 12]
    // nbins=10
    // method='mode'
    // bounds=[1 10]
    // levels=statelevels(x, nbins, method, bounds) 
    // See also
    // Authors
    // Jitendra Singh
    

   
    
    
  if or(type(x)==10) then
    error ('Input arguments must be double.')
end 
if size(x,2)==1 | size(x,1)==1 then
else
    error("Input x should be a vector");    
end
if length(x) < 2 then // checking the length of input datasat
  error('X must be a vector with more than one element.'); // if length of X is less 2, it will give error
end

if length(varargin)>5 then
    error('Wrong number on input arguments.')
end

if length(varargin)==0 then
     nbins=100;   // defining the default value of no of bins
    method='mode'; // defing the defualt method 'mode'
    bounds=[min(x) max(x)]; 
    fig='off';
end


if length(varargin)==1 then
 
    if varargin(1) =='fig' then
        error('input argument fig required a values.')
    else
           nbins=varargin(1);
 method='mode'; // defing the defualt method 'mode'
    bounds=[min(x) max(x)]; 
    fig='off'; 
        
        end
end


if length(varargin)==2 then
    nbins=100;
     fig='off'; 
    bounds=[min(x) max(x)];    
    method='mode';
    if varargin(1)=='fig'
        fig=varargin(2)
    elseif varargin(2)=='fig' then                      
    nbins=varargin(1);
    error ('input argument fig required a values.')
    
elseif varargin(1)~='fig' & varargin(2)~='on' | varargin(2)~='off' then
    nbins=varargin(1);
    method=varargin(2);
    
end
 
end


if length(varargin)==3 then
    nbins=varargin(1);
    method='mode';
    bounds=[min(x) max(x)];
    fig='off';    
    if varargin(2)== 'fig' then
        fig=varargin(3)
    elseif varargin(3)=='fig' then   
        error ('input argument fig required a values.')
        else 
        method=varargin(2);
        bounds=varargin(3);
    end 
       
    
    end       


if length(varargin)==4 then
    nbins=varargin(1);
    method=varargin(2);
    bounds=[min(x) max(x)];
    fig='off';
    
     if varargin(3)=='fig' then
         fig=varargin(4)
     elseif varargin(4)=='fig' then
          error ('input argument fig required a values.')
      elseif varargin(4)~='fig' then
          error('Unexpected input argument.')
          else
         bounds=varargin(3);
     end
 
end


if length(varargin)==5 then
     nbins=varargin(1);
    method=varargin(2);
    bounds=varargin(3);
    if varargin(4)=='fig' then
        fig=varargin(5);
    else
        error('Wrong input argument.')
    end

end


    if and(x==0) then     
        levels=zeros(1,2)
        histogram1=13;
        xx=zeros(1, (nbins-1));
        histogram=[histogram1,xx];
        bins=zeros(1,nbins);
          
        else

 if type(nbins)==10 then  // checking, if nbins if numeric aur charactr
    error ('Expected NBINS to be one of these types: double, Instead its type was char.');
    end  
if pmodulo(nbins,1)==0 then // checking, if nbins is integert or not
else
    error ('Size inputs must be integers.')
end

if length(nbins)~=1 then
    error('Expected NBINS to be a scalar.')
end



      if method == 'mode' | method == 'mean' then  // method should be either mean or mode
        else 
     error('Expected METHOD to match one of these strings: mean or mode');
           end
           

 
 
 if type(bounds)==10 then  // checking, if nbins if numeric aur charactr
    error ('Expected BOUNDS to be one of these types: double, Instead its type was char.');
end 

if length(bounds)~=2 then
    s=size(bounds);
    error(strcat(["Expected BOUNDS to be of size 1x2 when it is actually size", " ", string(s(1)), "x", string(s(2))]))
end


//if bounds(2)>0 | bounds (1)>0 then
//
//if bounds(2)>bounds(1) then
//     lower=bounds(1)
// upper=bounds(2);
//    else
//    error('BOUNDS must be strictly increasing.')
//end
//end

if bounds(2)<=bounds(1) then
    error('BOUNDS must be strictly increasing.')
else
    lower=bounds(1);
    upper=bounds(2);
end

if  bounds(2)==0 & bounds (1)==0 then
     lower=0;
 upper=0;
end
 
  if fig == 'off' | fig == 'on' then  // method should be either mean or mode
        else 
     error('Expected fig to match one of these strings: on or off');
           end

  denomm = upper-lower;
  if denomm==0 then
    denomm = 2.220D-16 ;
  end
  
  idx = nbins * (x-lower)/denomm;  
  idx = ceil(idx) + (idx==0);
  idx = idx(idx>=1 & idx<=nbins);
  histo = zeros(nbins, 1);
  for i=1:length(idx)
    histo(idx(i)) = histo(idx(i)) + 1; // calculationf histogram
  end
  

  

dy = (upper - lower) / length(histo);
index=find(histo>0);

if isempty(index) then
   iLowerRegion=[] 
    iUpperRegion=[]

else
  nn=length(index);
  iLowerRegion = index(1);
 
  iUpperRegion = index(nn);
end

  if isempty(iLowerRegion) | isempty(iUpperRegion) then
    levels = ['NaN' 'NaN'];
  else
   
        
    iLow  = iLowerRegion(1);
    iHigh = iUpperRegion(1);

    // define the lower and upper histogram regions halfway
    //between the lowest and highest nonzero bins.    
    lLow  = iLow;
    lHigh = iLow + floor((iHigh - iLow)/2);
    uLow  = iLow + floor((iHigh - iLow)/2);
    uHigh = iHigh;

    lHist = histo(lLow:lHigh); // defing lower and upper histogram
    uHist = histo(uLow:uHigh);
       
      levels = zeros(1,2);
       if (method == 'mode') then // if method is mode, calculate upper and lower levels
     [j iMax] = max(lHist);
      [k iMin] = max(uHist);
      levels(1) = lower + dy * (lLow + iMax(1) - 1.5);
      levels(2) = lower + dy * (uLow + iMin(1) - 1.5);
       elseif (method=='mean') then  // if method is mean, calculate lower and upper levels
           levels(1) = lower + dy * sum(((lLow:lHigh)-0.5).* (lHist)') / sum(lHist);
      levels(2) = lower + dy * sum(((uLow:uHigh)-0.5).* (uHist)') / sum(uHist);
       end
      
      // calculation bins
      
  end

 histogram=histo;  
      bins = lower + ((1:nbins) - 0.5)' * (upper - lower) / nbins; 
      


  if fig=='on' then // if the defined output is only 1, the it will provide the graphical representation of                          //levels
      
      if levels(1)=='NaN' | levels(2)=='NaN' then
          subplot(2,1,1)  
          plot(x, '-k', 'LineWidth',2)
             xlabel("Samples", "fontsize",3, "color", "black" )
      ylabel("Level (Volts)", "fontsize",3, "color", "black" )
      title("Signal",  "fontsize",3)
      
       subplot(2,1,2)
       plot(bins,histogram, '-k', 'LineWidth',2)
       xlabel("Level (Volts)", "fontsize",3, "color", "black" )
      ylabel("Count", "fontsize",3, "color", "black" )
           title("Histogram of the signal levels", "fontsize",3)
           
         else 
      subplot(2,1,1)
      plot(x, '-k', 'LineWidth',2)
      plot([1 length(x)],levels(1) * [1 1],'-.r', 'LineWidth',2)
      plot([1 length(x)],levels(2) * [1 1],'-.r', 'LineWidth',2)
      xlabel("Samples", "fontsize",3, "color", "black" )
      ylabel("Level (Volts)", "fontsize",3, "color", "black" )
      title("Signal",  "fontsize",3)
      
      subplot(2,1,2)
      plot(bins,histogram, '-k', 'LineWidth',2)
       xlabel("Level (Volts)", "fontsize",3, "color", "black" )
      ylabel("Count", "fontsize",3, "color", "black" )
      
      title("Histogram of the signal levels", "fontsize",3)
      end
  end
   end
      
      
  endfunction