bcr.m

临床医药试验随机数的产生（Biased Coin Randomization)

%Biased Coin Randomization%

%Source of Formulas:p9-10,Chapter 6STA 526%
%Three Different candidate versions of Formulas:1)Efron's; 2)Soares&Wu's;
%3)Chen's%


function x=bcr(version,sample_size,v,c);
%version:0:Efron's;1:S&W's;2:Chen's%

%sample_size%

%v: The new specified probability specified in Efron's and Chen's version
%0.5=<v<=1;%

%c:A prespecified constant c;used in S&W's and Chen's version%

if version==0; %Efron's version%
    
x(1)=binornd(1,0.5);
for i=2:sample_size;
    d=(2*sum(x))-(i-1);
    if d==0;
        x(i)=binornd(1,0.5);
    elseif d<0;
        x(i)=binornd(1,v);
    else
        x(i)=binornd(1,1-v);
    end
end

elseif version==1;%Soares and Wu's version%
   
    x(1)=binornd(1,0.5);
for i=2:sample_size;
    d=(2*sum(x))-(i-1);
    if abs(d)<c;
        x(i)=binornd(1,0.5);
    elseif d==c;
        x(i)=binornd(1,0);
    elseif d==-c
        x(i)=binornd(1,1);
    end
end
    
else %chen's version%
   
    x(1)=binornd(1,0.5);
for i=2:sample_size;
    d=(2*sum(x))-(i-1);
    if d==0;
        x(i)=binornd(1,0.5);
    elseif d==c;
        x(i)=binornd(1,0);
    elseif d==-c
        x(i)=binornd(1,1);
    elseif d>0&&d<c;
        x(i)=binornd(1,v);
    elseif d>-c&&d<0;
        x(i)=binornd(1,1-v);
        
        end
end
end