TrialSimulator (version 1.7.0)

DynamicRNGFunction: A wrapper of random number generator.

Description

This function may be useful to advanced users of TrialSimulator. It creates a wrapper function of a random number generator, while fixing a subset or all of arguments. This function is design to prevent inadvertent changing to arguments of random number generator. See examples below.

Usage

DynamicRNGFunction(fn, ...)

Value

a function to generate random number based on fn and arguments in .... Specified arguments will be fixed and cannot be changed when invoking DynamicRNGFunction(fn, ...)(). For example, if foo <- DynamicRNGFunction(rnorm, sd = 2), then foo(n = 100) will always generate data from normal distribution of variance 4. foo(n = 100, sd = 1) will trigger an error. However, if an argument is not specified in DynamicRNGFunction, then it can be specified later. For example, foo(n = 100, mean = -1) will generate data from N(-1, 4).

Arguments

fn

random number generator, e.g., rnorm, rchisq, etc. It can be user-defined random number generator as well, e.g., PiecewiseConstantExponentialRNG.

...

arguments for fn. Specifying invalid arguments can trigger error and be stopped. There are three exceptions. (1) rng can be passed through ... to give true name of fn. This could be necessary as it may be hard to parse it accurately in DynamicRNGFunction, or simply for a more informative purpose in some scenarios. (2) var_name can be passed through ... to specify the name of generated variable. (3) simplify can be set to FALSE to convert a vector into a one-column data frame in returned object. This happens for built-in random number generators, e.g., rnorm, rbinom, etc. These three arguments will not be passed into fn.

Examples

# example code
dfunc <- DynamicRNGFunction(rnorm, sd = 3.2)
x <- dfunc(1e3) # mean 0 and sd 3.2
hist(x)

y <- dfunc(1e3, mean = 3.5) # mean can be changed
mean(y)

try(z <- dfunc(1e3, sd = 1)) # error because sd is fixed in dfunc