Coerce an object to a <dist_spec>

Converts other representations of a probability distribution into a <dist_spec>. A <dist_spec> is returned unchanged. A numeric vector is interpreted as a probability mass function and becomes a NonParametric() distribution; a single number becomes a Fixed() point mass at that value.

Other packages can provide methods for their own distribution classes by registering an as_dist_spec.<class> method, without distspec depending on them or them re-implementing the <dist_spec> format.

Usage

as_dist_spec(x, ...)

# S3 method for class 'dist_spec'
as_dist_spec(x, ...)

# S3 method for class 'numeric'
as_dist_spec(x, ...)

# Default S3 method
as_dist_spec(x, ...)

Arguments

x

Object to convert: a <dist_spec>, a single number, or a numeric vector representing a probability mass function (zero-indexed, i.e. the first entry is the mass at zero; normalised to sum to one).

...

Additional arguments passed to methods. Every method forwards them to bound_dist() (directly for a <dist_spec>, via the constructor otherwise), so limits such as max apply regardless of the input class.

Value

A <dist_spec>.

See also

Distributions for the constructors this converts to.

Examples

# a PMF vector becomes a nonparametric distribution
as_dist_spec(c(0.1, 0.4, 0.3, 0.2))
#> - nonparametric distribution
#>   PMF: [0.1 0.4 0.3 0.2]

# a single number becomes a fixed (point mass) distribution
as_dist_spec(3)
#> - fixed value:
#>   3

# a <dist_spec> is returned unchanged
as_dist_spec(Gamma(mean = 4, sd = 1))
#> - gamma distribution:
#>   shape:
#>     16
#>   rate:
#>     4