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+% This programm reads ECG data which are saved in format 212.
+% (e.g., 100.dat from MIT-BIH-DB, cu01.dat from CU-DB,...)
+% The data are displayed in a figure together with the annotations.
+% The annotations are saved in the vector ANNOT, the corresponding
+% times (in seconds) are saved in the vector ATRTIME.
+% The annotations are saved as numbers, the meaning of the numbers can
+% be found in the codetable "ecgcodes.h" available at www.physionet.org.
+%
+% ANNOT only contains the most important information, which is displayed
+% with the program rdann (available on www.physionet.org) in the 3rd row.
+% The 4th to 6th row are not saved in ANNOT.
+%
+%
+%      created on Feb. 27, 2003 by
+%      Robert Tratnig (Vorarlberg University of Applied Sciences)
+%      (email: rtratnig@gmx.at),
+%
+%      algorithm is based on a program written by
+%      Klaus Rheinberger (University of Innsbruck)
+%      (email: klaus.rheinberger@uibk.ac.at)
+%
+%-------------------------------------------------------------------------
+clc; clear all;
+
+%------ SPECIFY DATA ------------------------------------------------------
+%------ 指定数据文件 -------------------------------------------------------
+PATH= 'F:\MATLAB\MIT-BIH'; % 指定数据的储存路径
+HEADERFILE= '100.hea';      % .hea 格式，头文件，可用记事本打开
+ATRFILE= '100.atr';         % .atr 格式，属性文件，数据格式为二进制数
+DATAFILE='100.dat';         % .dat ¸ñʽ£¬ECG Êý¾Ý
+SAMPLES2READ=1800;          % 指定需要读入的样本数
+                            % 若.dat文件中存储有两个通道的信号:
+                            % 则读入 2*SAMPLES2READ 个数据 
+
+%------ LOAD HEADER DATA --------------------------------------------------
+%------ 读入头文件数据 -----------------------------------------------------
+%
+% 示例：用记事本打开的117.hea 文件的数据
+%
+%      117 2 360 650000
+%      117.dat 212 200 11 1024 839 31170 0 MLII
+%      117.dat 212 200 11 1024 930 28083 0 V2
+%      # 69 M 950 654 x2
+%      # None
+%
+%-------------------------------------------------------------------------
+fprintf(1,'\\n$> WORKING ON %s ...\n', HEADERFILE); % 在Matlab命令行窗口提示当前工作状态
+% 
+% 【注】函数 fprintf 的功能将格式化的数据写入到指定文件中。
+% ±í´ïʽ£ºcount = fprintf(fid,format,A,...)
+% 在字符串'format'的控制下，将矩阵A的实数数据进行格式化，并写入到文件对象fid中。该函数返回所写入数据的字节数 count。
+% fid 是通过函数 fopen 获得的整型文件标识符。fid=1，表示标准输出（即输出到屏幕显示）；fid=2，表示标准偏差。
+%
+signalh= fullfile(PATH, HEADERFILE);    % 通过函数 fullfile 获得头文件的完整路径
+fid1=fopen(signalh,'r');    % 打开头文件，其标识符为 fid1 ，属性为'r'--“只读”
+z= fgetl(fid1);             % 读取头文件的第一行数据，字符串格式
+A= sscanf(z, '%*s %d %d %d',[1,3]); % 按照格式 '%*s %d %d %d' 转换数据并存入矩阵 A 中
+nosig= A(1);    % 信号通道数目
+sfreq=A(2);     % 数据采样频率
+clear A;        % 清空矩阵 A ，准备获取下一行数据
+for k=1:nosig           % 读取每个通道信号的数据信息
+    z= fgetl(fid1);
+    A= sscanf(z, '%*s %d %d %d %d %d',[1,5]);
+    dformat(k)= A(1);           % 信号格式; 这里只允许为 212 格式
+    gain(k)= A(2);              % 每 mV 包含的整数个数
+    bitres(k)= A(3);            % 采样精度（位分辨率）
+    zerovalue(k)= A(4);         % ECG 信号零点相应的整数值
+    firstvalue(k)= A(5);        % 信号的第一个整数值 (用于偏差测试)
+end;
+fclose(fid1);
+clear A;
+
+%------ LOAD BINARY DATA --------------------------------------------------
+%------ 读取 ECG 信号二值数据 ----------------------------------------------
+%
+if dformat~= [212,212], error('this script does not apply binary formats different to 212.'); end;
+signald= fullfile(PATH, DATAFILE);            % 读入 212 格式的 ECG 信号数据
+fid2=fopen(signald,'r');
+A= fread(fid2, [3, SAMPLES2READ], 'uint8')';  % matrix with 3 rows, each 8 bits long, = 2*12bit
+fclose(fid2);
+% 通过一系列的移位（bitshift）、位与（bitand）运算，将信号由二值数据转换为十进制数
+M2H= bitshift(A(:,2), -4);        %字节向右移四位，即取字节的高四位
+M1H= bitand(A(:,2), 15);          %取字节的低四位
+PRL=bitshift(bitand(A(:,2),8),9);     % sign-bit   取出字节低四位中最高位，向右移九位
+PRR=bitshift(bitand(A(:,2),128),5);   % sign-bit   取出字节高四位中最高位，向右移五位
+M( : , 1)= bitshift(M1H,8)+ A(:,1)-PRL;
+M( : , 2)= bitshift(M2H,8)+ A(:,3)-PRR;
+if M(1,:) ~= firstvalue, error('inconsistency in the first bit values'); end;
+switch nosig
+case 2
+    M( : , 1)= (M( : , 1)- zerovalue(1))/gain(1);
+    M( : , 2)= (M( : , 2)- zerovalue(2))/gain(2);
+    TIME=(0:(SAMPLES2READ-1))/sfreq;
+case 1
+    M( : , 1)= (M( : , 1)- zerovalue(1));
+    M( : , 2)= (M( : , 2)- zerovalue(1));
+    M=M';
+    M(1)=[];
+    sM=size(M);
+    sM=sM(2)+1;
+    M(sM)=0;
+    M=M';
+    M=M/gain(1);
+    TIME=(0:2*(SAMPLES2READ)-1)/sfreq;
+otherwise  % this case did not appear up to now!
+    % here M has to be sorted!!!
+    disp('Sorting algorithm for more than 2 signals not programmed yet!');
+end;
+clear A M1H M2H PRR PRL;
+fprintf(1,'\\n$> LOADING DATA FINISHED \n');
+
+%------ LOAD ATTRIBUTES DATA ----------------------------------------------
+atrd= fullfile(PATH, ATRFILE);      % attribute file with annotation data
+fid3=fopen(atrd,'r');
+A= fread(fid3, [2, inf], 'uint8')';
+fclose(fid3);
+ATRTIME=[];
+ANNOT=[];
+sa=size(A);
+saa=sa(1);
+i=1;
+while i<=saa
+    annoth=bitshift(A(i,2),-2);
+    if annoth==59
+        ANNOT=[ANNOT;bitshift(A(i+3,2),-2)];
+        ATRTIME=[ATRTIME;A(i+2,1)+bitshift(A(i+2,2),8)+...
+                bitshift(A(i+1,1),16)+bitshift(A(i+1,2),24)];
+        i=i+3;
+    elseif annoth==60
+        % nothing to do!
+    elseif annoth==61
+        % nothing to do!
+    elseif annoth==62
+        % nothing to do!
+    elseif annoth==63
+        hilfe=bitshift(bitand(A(i,2),3),8)+A(i,1);
+        hilfe=hilfe+mod(hilfe,2);
+        i=i+hilfe/2;
+    else
+        ATRTIME=[ATRTIME;bitshift(bitand(A(i,2),3),8)+A(i,1)];
+        ANNOT=[ANNOT;bitshift(A(i,2),-2)];
+   end;
+   i=i+1;
+end;
+ANNOT(length(ANNOT))=[];       % last line = EOF (=0)
+ATRTIME(length(ATRTIME))=[];   % last line = EOF
+clear A;
+ATRTIME= (cumsum(ATRTIME))/sfreq;
+ind= find(ATRTIME <= TIME(end));
+ATRTIMED= ATRTIME(ind);
+ANNOT=round(ANNOT);
+ANNOTD= ANNOT(ind);
+
+%------ DISPLAY DATA ------------------------------------------------------
+figure(1); clf, box on, hold on
+plot(TIME, M(:,1),'r');
+if nosig==2
+    plot(TIME, M(:,2),'b');
+end;
+for k=1:length(ATRTIMED)
+    text(ATRTIMED(k),0,num2str(ANNOTD(k)));
+end;
+xlim([TIME(1), TIME(end)]);
+xlabel('Time / s'); ylabel('Voltage / mV');
+string=['ECG signal ',DATAFILE];
+title(string);
+fprintf(1,'\\n$> DISPLAYING DATA FINISHED \n');
+
+% -------------------------------------------------------------------------
+fprintf(1,'\\n$> ALL FINISHED \n');
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