Vectorized structured sample

## Usage

`.str.sample(x, sp, resu, fr_prob)`

## Arguments

- x
vector containing sample size (i.e. richness) in the first element
and probabilities on the remaining

- sp
elements to be sampled

- resu
vector of results, must be the same length of sp

- fr_prob
Frequency or probability of each sp element. This will be multiplied by the
probability vector

## Value

vector of sampled sp elements

## Author

Neander Marcel Heming