MATLAB: Do we set r=r+1 when (x(t)-rang​eX(r))*(x(​t)-rangeX(​r+1))>0 in the uniform variables code

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a=3;
b=7; 
T=10^6; 
BinW=0.01;
x=zeros(1,T); 
rangeX=3:BinW:7;
Count=zeros(1,length(rangeX)-1); 
for t=1:T    
    
    u=rand(1);
        
    x(t)=a+(b-a)*u
        
    r=1;  
        
    while (x(t)-rangeX(r))*(x(t)-rangeX(r+1))>0  
            
        r=r+1;   
        
    end
        
    Count(r)=Count(r)+1; 
end
bar(rangeX(1:length(rangeX)-1),Count); 
axis([2.5 7.5 0 3000]);
I get this code from the class,and this code is about the uniform variables,in this code,i have some lines that i don't understand ,i hope someone can explain them to me.
1.
Count=zeros(1,length(rangeX)-1);
why do we create the 1 by length(rangeX)-1 zero matrix first,but not 1 by length(rangeX) zero matrix ?
2.
while (x(t)-rangeX(r))*(x(t)-rangeX(r+1))>0  
       
    r=r+1;   
end
I don't understand the meaning of these three lines code,why do we set r=r+1 when (x(t)-rangeX(r))*(x(t)-rangeX(r+1))>0

Best Answer

while (x(t)-rangeX(r))*(x(t)-rangeX(r+1))>0
is the cheking if x(t) is not in
its the same as:
while ~( rangeX(r) < x(t) &&  x(t) < rangeX(r+1) )
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