# Rev Language Reference

## dnHalfNormal - half-Normal Distribution

half-normal (gaussian) distribution with offset equal to ‘offset’ and standard deviation equal to ‘sd’.

### Usage

dnHalfNormal(Real offset, RealPos sd)

### Arguments

 offset : Real (pass by const reference) The offset parameter. sd : RealPos (pass by const reference) The standard deviation parameter.

### Details

The half-normal distribution has density: f(x) = 2/(sqrt(2 pi) sigma) e^-((x - offset)^2/(2 sigma^2)) where offset is the offset of the distribution and sigma the standard deviation. f(x) = 2/(sqrt(2 pi) sigma) e^-((x - offset)^2/(2 sigma^2)) where offset is the offset of the distribution and sigma the standard deviation.

### Example

# we simulate some oversations
x <- rhalfNormal(n=10,offset=0,sd=10)
# let's see what the minimum is (you could do the max too)
# the minimum should never be less than the offset
min(x)
# let's also see what the mean and the variance are
mean(x)
var(x)
sd(x)