function [s, sIdx] = pnExtractField(data,fieldName)
%PNEXTRACTFIELD Extract data for a single variable
% [ s, sIdx ] = pnExtractField(data,fieldName) extracts only the given
% field name for the data provided. The data is assumed to be in one of
% two forms: a cell array with each row as an individual field or a
% structure with each observation as an individual field (see below).
% The output, s, is in the same format, with all data but the desired
% field removed.
% sIdx are the indices used to extract this field from the original data.
%
%
% 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).
%
% OR
%
% data - Structure with each field being a new observation
% Each field should contain a cell array of the following format:
% Column 1 - Time stamp vectors for each subject
% Column 2 - Feature name vectors for each subject
% Column 3 - Data value vectors for each subject
%
%
% Outputs:
% s - Cell array of only fieldName 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
% 'PaFi')
% Column 4 - Data value vectors for each subject
% Empty cells indicate no available measurements (missing data).
%
% OR
%
% s - Structure with each field being a new observation
% Each field containS a cell array of the following format:
% Column 1 - Time stamp vectors for each subject
% Column 2 - Feature name vectors for each subject (only
% fieldName will be present)
% Column 3 - Data value vectors for each subject
%
% sIdx - Cell array of indices used for each observation to extract
% the data.
%
% Example
% %=== Load data in
% load('data_processed_cell.mat');
%
% %=== Extract pH
% [ pH ] = pnExtractField(data,'pH');
%
% See also PNLOADTEXTFILESCELL PNMAIN
% Copyright 2012 Alistair Johnson
% $LastChangedBy: alistair $
% $LastChangedDate: 2012-04-24 22:39:24 +0100 (Tue, 24 Apr 2012) $
% $Revision: 342 $
% Originally written on PCWIN64 by Alistair Johnson, 07-Mar-2012 18:16:23
% Contact: alistairewj@gmail.com
if isstruct(data)
%=== Create structure containing indices of each parameter
fn = fieldnames(data);
sIdx = structfun(@(x) strcmp(x(:,2),fieldName),data, 'UniformOutput',false);
s = struct();
for k=1:length(fn)
s.(fn{k}) = data.(fn{k})(sIdx.(fn{k}));
end
else
%=== Cell array format
sIdx = cellfun(@(x) strcmp(x,fieldName), data(:,3), 'UniformOutput',false);
s=[data(:,1), cellfun(@(x,y) x(y), data(:,2:end), repmat(sIdx,1,3),'UniformOutput',false)];
end
end