How Can I vectorize the following codes?

Question

Monkeydongkey 2015-9-15

关闭： MATLAB Answer Bot 2021-8-20

for i=1:40, A(i,2); end
for j=1:100, x(j)=1/j; end
s=0; for k=1:100, s=s+rand; end

I think for the second one, it should be something like

j=1:100;x(j)=1/j; ?

can anyone help me?

Answer 1

Walter Roberson 2015-9-15

The first one

for i=1:40, A(i,2); end

can be vectorized as:

;

That is, it does not do anything, unless you count the checking to be sure that A(i,2) exists.

The second one is

x = 1 ./ (1:100);

or

j = 1:100; x = 1./j;

Or if you need to be strict about the possibility that x already exists and might be larger than 100 elements,

j = 1:100; x(j) = 1./j;

The third one is

s = sum(rand(1,100));