How to set the default seed for the RNG behind the runif(), sample() and other command? Well, there are several ways doing that (like setting .Random.seed directly), but as the documentation states, set.seed() is the recommended way to specify seeds.

> ?set.seed
> set.seed(0)
> runif(1,0,1)
[1] 0.8966972
> set.seed(0)
> runif(1,0,1)
[1] 0.8966972

> set.seed(0)
> sample(1:10, 10)
 [1]  9  3 10  5  6  2  4  8  7  1
> sample(1:10, 10)
 [1]  1  2  9  5  3  4  8  6  7 10
> set.seed(0)
> sample(1:10, 10)
 [1]  9  3 10  5  6  2  4  8  7  1
> sample(1:10, 10)
 [1]  1  2  9  5  3  4  8  6  7 10

BTW runif() stands for random uniform, not a “run if…” branching expression. Tricky naming conventions 😉

Further reading

• David Smith’s blog post at Revolution Analytics
• > ?set.seed
• > ?runif
• > ?sample