Hi guys, I am starting to study about time-series analysis... I am now in the Pearson coefficient of autocorrelation... Is this the same with the ACF() function? I have the following from a manual, but I don't understand how they got the output (located at the bottom). Can you guys tell me how they got

Here are the details:
Function: acf()
Purpose Computes sample autocorrelations.
Format rk = acf(y,k,d);
y Nx1 vector, data.
k scalar, maximum number of autocorrelations to compute.
d scalar, order of differencing.


I have the following data:
x = { 20.80,
18.58,
23.39,
20.47,
21.78,
19.56,
19.58,
18.91,
20.08,
21.88 };

rk = acf(x,4,2);
print rk;

OUTPUT:
-0.74911771
0.48360914
-0.34229330
0.17461180

I would appreciate some help.