Description Usage Arguments Details Value Note Author(s) References See Also Examples

View source: R/simulateVector.R

Simulate a vector of random numbers from a specified theoretical probability distribution or empirical probability distribution, using either Latin Hypercube sampling or simple random sampling.

1 2 3 4 |

`n` |
a positive integer indicating the number of random numbers to generate. |

`distribution` |
a character string denoting the distribution abbreviation. The default value is
Alternatively, the character string |

`param.list` |
a list with values for the parameters of the distribution.
The default value is Alternatively, if you specify an empirical distribution by setting |

`sample.method` |
a character string indicating whether to use simple random sampling |

`seed` |
integer to supply to the |

`sorted` |
logical scalar indicating whether to return the random numbers in sorted
(ascending) order. The default value is |

`left.tail.cutoff` |
a scalar between 0 and 1 indicating what proportion of the left-tail of
the probability distribution to omit for Latin Hypercube sampling.
For densities with a finite support minimum (e.g., Lognormal or
Empirical) the default value is |

`right.tail.cutoff` |
a scalar between 0 and 1 indicating what proportion of the right-tail of
the probability distribution to omit for Latin Hypercube sampling.
For densities with a finite support maximum (e.g., Beta or
Empirical) the default value is |

**Simple Random Sampling** (`sample.method="SRS"`

)

When `sample.method="SRS"`

, the function `simulateVector`

simply
calls the function `r`

*abb*, where *abb* denotes the
abbreviation of the specified distribution (e.g., `rlnorm`

,
`remp`

, etc.).

**Latin Hypercube Sampling** (`sample.method="LHS"`

)

When `sample.method="LHS"`

, the function `simulateVector`

generates
`n`

random numbers using Latin Hypercube sampling. The distribution is
divided into `n`

intervals of equal probability *1/n* and simple random
sampling is performed once within each interval; i.e., Latin Hypercube sampling
is simply stratified sampling without replacement, where the strata are defined
by the 0'th, 100(1/n)'th, 100(2/n)'th, ..., and 100'th percentiles of the
distribution.

** Latin Hypercube sampling**, sometimes abbreviated

See Millard (2013) for a visual explanation of Latin Hypercube sampling.

a numeric vector of random numbers from the specified distribution.

** Latin Hypercube sampling**, sometimes abbreviated

Steven P. Millard ([email protected])

Iman, R.L., and W.J. Conover. (1980). Small Sample Sensitivity Analysis
Techniques for Computer Models, With an Application to Risk Assessment
(with Comments). *Communications in Statistics–Volume A, Theory and Methods*,
**9**(17), 1749–1874.

Iman, R.L., and J.C. Helton. (1988). An Investigation of Uncertainty and
Sensitivity Analysis Techniques for Computer Models. *Risk Analysis*
**8**(1), 71–90.

Iman, R.L. and J.C. Helton. (1991). The Repeatability of Uncertainty and
Sensitivity Analyses for Complex Probabilistic Risk Assessments.
*Risk Analysis* **11**(4), 591–606.

McKay, M.D., R.J. Beckman., and W.J. Conover. (1979). A Comparison of Three
Methods for Selecting Values of Input Variables in the Analysis of Output
From a Computer Code. *Technometrics* **21**(2), 239–245.

Millard, S.P. (2013). *EnvStats: an R Package for Environmental Statistics*.
Springer, New York. http://www.springer.com/book/9781461484554.

Vose, D. (2008). *Risk Analysis: A Quantitative Guide*. Third Edition.
John Wiley & Sons, West Sussex, UK, 752 pp.

Probability Distributions and Random Numbers, Empirical,
`simulateMvMatrix`

, `set.seed`

.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | ```
# Generate 10 observations from a lognormal distribution with
# parameters mean=10 and cv=1 using simple random sampling:
simulateVector(10, distribution = "lnormAlt",
param.list = list(mean = 10, cv = 1), seed = 47,
sort = TRUE)
# [1] 2.086931 2.863589 3.112866 5.592502 5.732602 7.160707
# [7] 7.741327 8.251306 12.782493 37.214748
#----------
# Repeat the above example by calling rlnormAlt directly:
set.seed(47)
sort(rlnormAlt(10, mean = 10, cv = 1))
# [1] 2.086931 2.863589 3.112866 5.592502 5.732602 7.160707
# [7] 7.741327 8.251306 12.782493 37.214748
#----------
# Now generate 10 observations from the same lognormal distribution
# but use Latin Hypercube sampling. Note that the largest value
# is larger than for simple random sampling:
simulateVector(10, distribution = "lnormAlt",
param.list = list(mean = 10, cv = 1), seed = 47,
sample.method = "LHS", sort = TRUE)
# [1] 2.406149 2.848428 4.311175 5.510171 6.467852 8.174608
# [7] 9.506874 12.298185 17.022151 53.552699
#==========
# Generate 50 observations from a Pareto distribution with parameters
# location=10 and shape=2, then use this resulting vector of
# observations as the basis for generating 3 observations from an
# empirical distribution using Latin Hypercube sampling:
set.seed(321)
pareto.rns <- rpareto(50, location = 10, shape = 2)
simulateVector(3, distribution = "emp",
param.list = list(obs = pareto.rns), sample.method = "LHS")
#[1] 11.50685 13.50962 17.47335
#==========
# Clean up
#---------
rm(pareto.rns)
``` |

EnvStats documentation built on Oct. 10, 2017, 1:05 a.m.

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