is.constant: Constant Vectors
In jsta/rv: Simulation-Based Random Variable Objects

Description Usage Arguments Details Value Author(s) References Examples

Functions to coerce or test for non-random objects.

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is.constant(x)

as.constant(x)

`x`	an object, random variable (rv) or not

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.

a logical vector (not rv), TRUE if a component is constant w.p. 1

Jouni Kerman jouni@kerman.com

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").

  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