%3B.  function to normalize data by arithmetic mean
%		normalization factors here are relative to the mean of all
%       spiked control signals
function normalized_data = AM_normalize(unnorm_data,missing_data,num_controls)
[num_rows, num_expt] = size(unnorm_data);

%find mean of all control signals
mean_controls = mean(mean(unnorm_data(1:num_controls,:)));

%calculate the ratio of each control to the mean control signal
control_ratios = mean(unnorm_data)./repmat(mean_controls,1,num_expt);

%normalize the data
normalized_data = unnorm_data./repmat(control_ratios,num_rows,1);

%set all missing values back to -1000
normalized_data(missing_data) = -1000;	
return