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## 10.6 Pseudorandom Number Generators

For most of the probability functions, there is a matching pseudorandom number generator (PRNG) with the suffix _rng. For example, the function normal_rng(real, real) accepts two real arguments, an unconstrained location $$\mu$$ and positive scale $$\sigma > 0$$, and returns an unconstrained pseudorandom value drawn from $$\text{Normal}(\mu,\sigma)$$. There are also vectorized forms of random number generators which return more than one random variate at a time.

### 10.6.1 Restricted to Transformed Data and Generated Quantities

Unlike regular functions, the PRNG functions may only be used in the transformed data or generated quantities block.

### 10.6.2 Limited Vectorization

Unlike the probability functions, only some of the PRNG functions are vectorized.