%PREWHITE    Removes the carrier fequencies of a given spectrogram
% Normalizes top 50% of frequencies based on power


%Shane Crockett 10JUN98
%Integrates each frequency WRT time and chooses the top 50% of frequencys based on total power of that row.

warning off													%turns off warning for future divide by zero
echo off	

[R C] = size(B);									% Determines size of h

int = mean(B,2);									% Computes avg. power by determining the mean of each freq. bin (by summing  
num = 1:length(int);							   	% each freq.bin and dividing by the # of elements in that bin.)

int(:,2) = num';									% Assigns a number to each value of average power

sort = sortrows(int,1);							% Sorts the values of avg. power and arranges them in ascending order - based on first column
sort = flipud(sort);								% Rearranges values of avg. power into descending order
x = round(length(int(:,1))/2);					% Determines how many frequency bins will be normalized

car = sort(1:x,2);									%
for n = car											% Creates a matrix of the top 50% freq. bins based on avg. power
   pre = zeros(length(int),C);		  			%
   row = B(n,:);									%
   pre(n,:) = row;									%
end
rB = reshape(B,1,R*C);
msort = sortrows(rB');
mbar = median(msort);									% Determines the median value for the entire spectrum 

normalize = mbar./mean(B')';						% Develops a matrix of normalized elements and replaces these normalized
w = 1 - isnan(pre./pre);							% freq bins into the original matrix.  Zero is divided by Zero and a warning 
for k = num;											% is generated but not displayed.
   prew(k,:) = normalize(k).*w(k,:);			%
end														%
supcar = B.*prew + isnan(pre./pre).*B;			% New spectrum matrix with suppressed carriers

%clear prew;											% Erases PREW matrix
warning on											% Turns warnings back on

% Administrative to free space
clear R C B int num sort x car n pre row rB msort mbar w k prew normalize

%PLOTS SPECTROGRAM OF PREWHITENED DATA
prewspec
titl = ['Prewhitened Spectrogram of ' filename];
title(titl)