readedf_EX1.m

function [x,Fs,Start_date,Start_time,Label,Dimension,Coef,Nmb_chans,N] = readedf_EX1(fname,ch,t1,t2)

%	[x,Fs,Start_date,Start_time,Label,Dimension,Coef,Nmb_chans,N] = readedf(fname,channel,t1,t2)
%
%	Reads one channel from EDF-file in given time scale. Time scale may be given as seconds from
%	the beginning of the file or in hh:mm:ss format. In hh:mm:ss format, the hours of the next days
%	are accessed by adding 24h to the true time (e.g. 25:00:00 means 01:00:00 of the day following
%	the starting date of the recording).
%
%   in:	fname		file name OR file handle (empty -> file name is asked for)
%	ch		channel number, 1st channel being 0, or channel label (default 0)
%	t1		start time (seconds from the beginning of file OR hh:mm:ss) (default 0)
%	t2		end time (seconds from the beginning of file OR hh:mm:ss) (default one block)
%
%  out:	x		signal in column vector
%	Fs		sampling frequency
%	Start_date	Date of the starting time of the recording [dd:mm:yy]
%	Start_time	Time of the beginning of the recording [hh:mm:ss]
%	Label		Signal label
%	Dimension	Signal dimension
%	Coef		Scaling coefficients [PhysMin PhysMax DigMin DigMax]
%	Nmb_chans	Number of channels in the file
%	N		data length in seconds

%	(c) Ilkka Korhonen 13.2.1996 (20.2.1996 IKo) (16.10.1997 IKo) (22.10.1997 IKo fid/fname)
%	    Juha Pärkkä 10.7.1997, IKO 11.08.1998, IKo 26.11.1998, IKo 25.01.1999, IKo 21.07.1999
%	    IKo 05.10.1999, IKo 20.10.1999 (t2 inf), IKo 03.10.2000 (ch may be string)

if nargin<1;fname=[];end
if nargin<2;ch=0;end
if nargin<3;t1=0;end
if nargin<4;t2=[];end

% Check between file name / file handle
if length(fname)==1
	fid = fname;
elseif length(fname)==0
	[fname,pname]=uigetfile('*.rec','Select European Data Format file');
	fname = [pname fname];
	fid = fopen(fname,'r');
else
	fid = fopen(fname,'r');
end
if fid<0
	disp('Cannot open file !');
	return;
end
if isstr(ch)
        [Nmb_chans,Fs,Label] = edfhdr(fname);
        match_ch = [];
        for i=1:Nmb_chans
                if strncmp(lower(ch),lower(setstr(Label(i,:))),length(ch))
                        match_ch = [match_ch i-1];
                end
        end
        if length(match_ch)>1
                fprintf('Matching channels in the given EDF file:\n');
                for i=1:length(match_ch)
                        fprintf('Channel %d:\t%s\n',match_ch(i),setstr(Label(match_ch(i)+1,:)));
                end
                error('Only one channel should be given!');
        elseif length(match_ch)==0
                error('No such channel!');
        else
                ch = match_ch;
        end
        if length(fname)>1	% fname is not fid in function call; needs re-opening as edfhdr closes the file
                fid = fopen(fname,'r');
        end
end

% First scan the header information
	fseek(fid,168,-1);
	Start_date = setstr(fread(fid,8,'char')');
	Start_time = setstr(fread(fid,8,'char')');
	Hdr_size   = sscanf(setstr(fread(fid,8,'char')'),'%d');
	fseek(fid,52,0);
	Blck_size  = sscanf(setstr(fread(fid,8,'char')'),'%d');
	Nmb_chans  = sscanf(setstr(fread(fid,4,'char')'),'%d');

	current = ftell(fid);
	fseek(fid,ch*16,0);
	Label      = setstr(fread(fid,16,'char')');
	fseek(fid,current+Nmb_chans*16+Nmb_chans*80,-1);

	current = ftell(fid);
	fseek(fid,ch*8,0);
	Dimension  = setstr(fread(fid,8,'char')');
	fseek(fid,current+Nmb_chans*8,-1);

	current = ftell(fid);
	fseek(fid,ch*8,0);
	Phys_min  = sscanf(setstr(fread(fid,8,'char')'),'%f');
	fseek(fid,current+Nmb_chans*8,-1);

	current = ftell(fid);
	fseek(fid,ch*8,0);
	Phys_max  = sscanf(setstr(fread(fid,8,'char')'),'%f');
	fseek(fid,current+Nmb_chans*8,-1);

	current = ftell(fid);
	fseek(fid,ch*8,0);
	Dig_min   = sscanf(setstr(fread(fid,8,'char')'),'%d');
	fseek(fid,current+Nmb_chans*8,-1);

	current = ftell(fid);
	fseek(fid,ch*8,0);
	Dig_max   = sscanf(setstr(fread(fid,8,'char')'),'%d');
	fseek(fid,current+Nmb_chans*8+Nmb_chans*80,-1);

	Coef = [Phys_min Phys_max Dig_min Dig_max];
	
	Nmp_smps=zeros(1,Nmb_chans);
	for i=0:Nmb_chans-1
		Nmb_smps(i+1)  = sscanf(setstr(fread(fid,8,'char')'),'%d');
	end

% Calculate data length
	fseek(fid,0,'bof');
	pos0=ftell(fid);
	fseek(fid,0,'eof');
	pos1=ftell(fid);
	Data_rec = sum(Nmb_smps)*2;
	N = Blck_size*(pos1-pos0-Hdr_size)/Data_rec;

% Transform the start and end times to seconds if necessary
	if max(size(t1))>1
		t1 = hour2sec(t1) - hour2sec(Start_time);
	end
	if length(t2)>1
		t2 = hour2sec(t2) - hour2sec(Start_time);
	elseif isempty(t2)
		t2 = Blck_size;
        end
        if t2>N | isinf(t2);t2=N;end

% Then read the data
	Fs = Nmb_smps(ch+1)/Blck_size;
	x  = zeros(min([round(Fs*(t2-t1)) ceil(N*Fs)]),1);
	len = length(x);
	Skip = Data_rec-Nmb_smps(ch+1)*2;
	Blck_1 = fix(t1/Blck_size);		% 1st data block number
	block1 = Data_rec*Blck_1;
	Blck_N = fix(t2/Blck_size);		% Last data block number	

% 1st data block
	if (fseek(fid,Hdr_size+block1,-1)<0)
		x=[];return;
	end
	Blck_cnt = Blck_1;
	if ch~=0
		Skip_1 = sum(Nmb_smps(1:ch))*2;
	else
		Skip_1 = 0;
	end
	offset = round(rem(t1,Blck_size)*Fs)*2;
	if (fseek(fid,offset + Skip_1,0)<0)
		x=[];return;
	end
        if Blck_1==Blck_N 			% Read only within one block
                n2 = round(rem(t2,Blck_size)*Fs) - offset/2;
	else					% Read at least within two blocks
		n2 = Nmb_smps(ch+1) - offset/2;
        end
	x(1:n2) = fread(fid,n2,'int16');
% Next data blocks
	while (Blck_cnt<Blck_N-1)
		Blck_cnt = Blck_cnt+1;
		n1 = n2+1;
		n2 = n1+Nmb_smps(ch+1)-1;
                if (fseek(fid,Skip,0)==0)
                        x_tmp = fread(fid,Nmb_smps(ch+1),'int16');
                        if ~isempty(x_tmp);x(n1:n2) = x_tmp;end
                else
			break;
		end
	end
% Final data block
	if Blck_1 ~= Blck_N
                fseek(fid,Skip,0);
                pos0=ftell(fid);
                fseek(fid,0,'eof');
                pos1=ftell(fid);
		N_left = Blck_size*(pos1-pos0)/Data_rec;
		fseek(fid,pos0,'bof');
		n1 = n2+1;
                offset = round(rem(t2,Blck_size)*Fs);
                if offset>0
                        n2 = n1 + offset -1;
                        x_tmp = fread(fid,offset,'int16');
                        if length(x_tmp)==offset;x(n1:n2) = x_tmp;end
		end
        end
	
% Finally, scale the signal
a = polyfit([Dig_min Dig_max],[Phys_min Phys_max],1);
x = x*a(1)+a(2);

% Close file if file name is used instead of file handle
if length(fname)>1
	fclose(fid);
end