writing a loop for differences of random numbers.

hello, i needed to write a loop to create a vector of 1000 random numbers. then from there i needed to create a loop to subtract every random number, by ever other random number. basically generating a 1000x1000 vector. however i am lost at how to go about it. here is my code so far.

for i= 1:1000
  b(i) =rand;
  end

    for i =1:1000,
       c =b(i) - b(1:1000);

     end

Answer 1

[Mikhail]

%Generate: for i= 1:1000

b(i) =rand;

end

%Subtract:

c=zeros(1000,1000)

for i =1:1000

c(i,:)=b-b(i);

end

So in matrix c: c(i,j)=b(j)-b(i)

[Mikhail]

Also there is much faster way to generate those numbers, without for loop:

b=rand(1000,1);

[John D'Errico]

Of course, IF you were to generate the numbers in a vectorized form, it would also be far more efficient to use bsxfun to do the entire computation in two lines.

b = rand(1000,1);
c = bsxfun(@minus,b,b');

This of course, is the power of MATLAB, that explicit loops are not needed for simple computations like this.