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

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

Answer 1

[darova]

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) )    

[yang-En Hsiao]

so if x(t) is not between the rangeX(r) and rangeX(r+1),so.........what?why should i write this code?

[darova]

You shoudn't, just showed you an example.

if x(t) is not between that range we r = r+1 (we examine another range). And when x(t) is IN the range we quit from while loop.

In another words: we searching range for x(t)