rv (version 2.3.1)

constant: Constant Vectors

Description

Functions to coerce or test for non-random objects.

Usage

is.constant(x) as.constant(x) "as.constant"(x) "as.constant"(x)

Arguments

x

an object, random variable (rv) or not

Details

is.constant returns TRUE for each component of the argument object if there is only one simulation (that is, the variable is ``constant'').

Note: rv objects that merely have variance zero are not therefore necessarily ``true'' constants.

as.constant coerces rv or rvsummary objects into constant strings; NA is returned for component that is not random.

References

Kerman, J. and Gelman, A. (2007). Manipulating and Summarizing Posterior Simulations Using Random Variable Objects. Statistics and Computing 17:3, 235-244.

See also vignette("rv").

Examples

  is.constant(1)         # TRUE
  is.constant(as.rv(1))  # TRUE
  setnsims(200)
  x <- rvbern(prob=0.001)
  all(sims(x)==0)        # most probably true
  is.constant(x)         # always FALSE
  x <- rvnorm(3)
  x[1] <- 1
  as.constant(x)         # 1, NA, NA
  all(is.random(x) & is.na(as.constant(x))) # always TRUE