rethinking (version 2.13)

dstudent: Non-standard Student's t distribution

Description

Functions for computing density and producing random samples from a non-standardized Student's t distribution.

Usage

dstudent( x, nu = 2, mu = 0, sigma = 1, log = FALSE )
rstudent( n, nu = 2, mu = 0, sigma = 1 )

Arguments

x

Values to compute densities of

nu

Degrees of freedom (tail shape)

mu

Location of distribution (mean)

sigma

Scale of distribution

log

If TRUE, returns log-density instead of density

n

Number of random observations to sample

Details

These functions provide density and random number calculations for Student's t distribution, translated and scaled by mean mu and scale sigma. Note that sigma is not the distribution's standard deviation, unless nu is very large.

Examples

# NOT RUN {
library(rethinking)
data(WaffleDivorce)
d <- WaffleDivorce
d$A <- scale( d$MedianAgeMarriage )
d$D <- scale( d$Divorce )
d$M <- scale( d$Marriage )

m5.3b <- quap(
    alist(
        D ~ dstudent( 2 , mu , sigma ) ,
        mu <- a + bM*M + bA*A ,
        a ~ dnorm( 0 , 0.2 ) ,
        bM ~ dnorm( 0 , 0.5 ) ,
        bA ~ dnorm( 0 , 0.5 ) ,
        sigma ~ dexp( 1 )
    ) , data = d )
# }