sobol_dummy {sensobol}

Computation of Sobol' indices for a dummy parameter

Description

This function computes first and total-order Sobol' indices for a dummy parameter following the formulae shown in Khorashadi Zadeh et al. (2017).

Usage

sobol_dummy(
  Y,
  N,
  params,
  boot = FALSE,
  R = NULL,
  parallel = "no",
  ncpus = 1,
  conf = 0.95,
  type = "norm"
)

Arguments

Y

A numeric vector with the model output obtained from the matrix created with sobol_matrices. The numeric vector should not contain any NA or NaN values.

N

Positive integer, the initial sample size of the base sample matrix created with sobol_matrices.

params

A character vector with the name of the model inputs.

boot

Logical. If TRUE, the function bootstraps the Sobol' indices. If FALSE, it provides point estimates. Default is boot = FALSE.

R

Positive integer, number of bootstrap replicas.

parallel

The type of parallel operation to be used (if any). If missing, the default is taken from the option "boot.parallel" (and if that is not set, "no"). For more information, check the parallel option in the boot function of the boot package.

ncpus

Positive integer: number of processes to be used in parallel operation: typically one would chose this to the number of available CPUs. Check the ncpus option in the boot function of the boot package.

conf

Confidence intervals, number between 0 and 1. Default is conf = 0.95.

type

Method to compute the confidence intervals. Default is type = "norm". Check the type option in the boot function of the boot package.

Value

A data.table object.

References

Khorashadi Zadeh F, Nossent J, Sarrazin F, Pianosi F, van Griensven A, Wagener T, Bauwens W (2017). “Comparison of variance-based and moment-independent global sensitivity analysis approaches by application to the SWAT model.” Environmental Modelling and Software, 91, 210–222. doi:10.1016/j.envsoft.2017.02.001.

Examples

# Define settings
N <- 100; params <- paste("X", 1:3, sep = ""); R <- 10

# Create sample matrix
mat <- sobol_matrices(N = N, params = params)

# Compute Ishigami function
Y <- ishigami_Fun(mat)

# Compute and bootstrap Sobol' indices for dummy parameter
ind.dummy <- sobol_dummy(Y = Y, N = N, params = params, boot = TRUE, R = R)