Set it to "exactly" reproduce your results in the future or by others.
<br />
set.seed(42); s1=.Random.seed<br />
x=rnorm(100)<br />
set.seed(42); s2=.Random.seed<br />
y=rnorm(100)<br />
all.equal(x,y);<br />
all.equal(s1, s2); s3=.Random.seed<br />
z=rnorm(100)<br />
all.equal(y,z)<br />
all.equal(s2, s3)<br />
</p>
