function [ pac2 ] = pnPaC2(data)
%PNPAC2 Extract PaC2 from the data, measured as PaO2 / PaCO2
% [ pac2 ] = pnPaC2(data) calculates the "PaC2" from the data by taking
% the ratio of PaO2 and PaCO2 for each time point containing synchronous
% measurements of the two. The output is of the same form as
% PNEXTRACTFIELD.
%
%
% Inputs:
% data - Cell array of data inputs in standard format:
% Column 1 - Subject IDs
% Column 2 - Time stamp vectors for each subject
% Column 3 - Feature name vectors for each subject
% Column 4 - Data value vectors for each subject
% Empty cells indicate no available measurements (missing data).
%
% Outputs:
% pac2 - Cell array of only pac2 data in standard format:
% Column 1 - Subject IDs
% Column 2 - Time stamp vectors for each subject
% Column 3 - Feature name vectors for each subject (only contains
% 'PaC2')
% Column 4 - Data value vectors for each subject
% Empty cells indicate no available measurements (missing data).
%
% Example
% %=== Load data in
% load('data_processed_cell.mat');
%
% %=== Calculate score
% [ pac2 ] = pnPaC2(data);
%
% See also PNEXTRACTFIELD PNLOADTEXTFILESCELL PNIANDREW PNMAIN
% References:
% Physionet Challenge 2012
% http://physionet.org/challenge/2012/
% Copyright 2012 Alistair Johnson
% $LastChangedBy: alistair $
% $LastChangedDate: 2012-04-24 22:39:24 +0100 (Tue, 24 Apr 2012) $
% $Revision: 342 $
% Originally written on GLNXA64 by Alistair Johnson, 24-Apr-2012 14:02:09
% Contact: alistairewj@gmail.com
%=== PaC2 = PaO2 / PaCO2
pao2 = 'PaO2';
pao2 = pnExtractField(data,pao2);
paco2 = 'PaCO2';
paco2 = pnExtractField(data,paco2);
%=== For each record, extract PaO2 times and calculate PaCO2 at them
pac2 = cell(size(paco2));
pac2(:,1) = paco2(:,1); % subject ID
N = size(paco2,1);
for k=1:N
if isempty(pao2{k,2})
continue;
else
%=== Get times for pao2 and fio2
t1 = pao2{k,2}; t2 = paco2{k,2};
%=== Intersection
[t_impute,ti,tj] = intersect(t1,t2);
pac2{k,2} = t_impute;
pac2{k,3} = repmat({'PaC2'},numel(t_impute),1);
pac2{k,4} = pao2{k,4}(ti) ./ paco2{k,4}(tj);
end
end
end